Thursday, August 12, 2010

Patient information: Anaphylaxis symptoms and diagnosis

ANAPHYLAXIS OVERVIEW — Anaphylaxis is a potentially deadly allergic reaction that is rapid in onset. It is most often triggered by foods, medications, and insect stings. There are many other possible triggers.

Anaphylaxis is an unpredictable condition. Many people who experience it have a known allergy and some have had one or more milder allergic reactions previously. Others, who are not even aware that they have an allergy, can suddenly experience severe anaphylaxis. Even the first episode of anaphylaxis can be fatal.

The severity of anaphylactic reactions can be minimized by recognizing the symptoms early, having proper medication available for self-treatment, and seeking emergency medical care promptly. This topic reviews the symptoms and diagnosis of anaphylaxis. Treatment and prevention of anaphylaxis are discussed separately. A separate topic discusses how to use an epinephrine autoinjector. (See "Patient information: Anaphylaxis treatment and prevention" and see "Patient information: Use of an epinephrine autoinjector").

ANAPHYLAXIS SYMPTOMS — Symptoms of anaphylaxis generally begin within minutes to an hour of exposure to a trigger. Less commonly, symptoms do not develop for several hours.

The most common symptoms of anaphylaxis are hives (urticaria) and swelling of the skin (angioedema), which occur in 80 to 90 percent of reactions. Respiratory symptoms occur in about 50 percent of reactions, and are especially common in people who also have asthma or another chronic respiratory disease. Extremely low blood pressure, causing lightheadedness, dizziness, blurred vision, or loss of consciousness (passing out) occurs in about 30 percent of reactions.

Anaphylaxis can cause symptoms throughout the body: Skin: Itching, flushing, hives (urticaria), or swelling (angioedema) Eyes: Itching, tearing, redness, or swelling of the skin around the eyes Nose and mouth: Sneezing, runny nose, nasal congestion, swelling of the tongue, or a metallic taste Lungs and throat: Difficulty getting air in or out, repeated coughing, chest tightness, wheezing or other sounds of labored breathing, increased mucus production, throat swelling or itching, hoarseness, change in voice, or a sensation of choking Heart and circulation: Dizziness, weakness, fainting, rapid, slow, or irregular heart rate, or low blood pressure Digestive system: Nausea, vomiting, abdominal cramps, or diarrhea Nervous system: Anxiety, confusion, or a sense of impending doom

A severe form of anaphylaxis causes sudden collapse without other obvious symptoms, such as hives or flushing. This form of anaphylaxis occurs most commonly after a person is given a medication into a vein or is stung by an insect.

Up to 20 percent of people with anaphylaxis have biphasic (two-phase) or protracted (prolonged) anaphylaxis. A person with biphasic anaphylaxis has a reaction that resolves and then recurs hours later without further exposure to the trigger. The late phase reaction usually occurs within eight hours, but may occur up to 72 hours after the initial symptoms. A person with protracted anaphylaxis has signs and symptoms that persist for hours or even days despite treatment, although this is rare.

ANAPHYLAXIS TRIGGERS — The trigger for a person's anaphylaxis may be obvious or it may be difficult to identify.

Common anaphylaxis triggers can include: Foods: In children, hen's eggs, cow's milk, peanuts, tree nuts, fish, wheat, and soy are the most common food triggers.

In teens and adults, peanuts, tree nuts, fish, and crustaceans (shellfish such as shrimp) are the most common triggers.

Any food, including fruits and vegetables, and some spices and food additives, can cause anaphylaxis. Medications, especially certain antibiotics (such as penicillin or amoxicillin), medications for pain and fever (such as aspirin or ibuprofen), some x-ray dyes (also called radiocontrast media), and others Venom from insects, including bees, hornets, wasps, and fire ants Latex from natural rubber, found in some latex gloves, balloons, condoms, sports equipment, and medical products Allergen immunotherapy ("allergy shots"), such as those given for the treatment of allergic rhinitis (hay fever) Exercise, either by itself, or after eating certain foods (eg, wheat, celery, seafood), medications (eg, aspirin), or exposure to cold air/water Less common triggers include exposure to airborne allergens (such as horse dander), human seminal fluid, and cold temperatures.

Sometimes a specific trigger cannot be identified, even after a thorough evaluation. This condition is called idiopathic anaphylaxis. (See "Patient information: Anaphylaxis treatment and prevention").

IgE mediated anaphylaxis — In most people, anaphylaxis is caused by the presence of proteins called immunoglobulin E (IgE) antibodies. IgE antibodies are normally produced in the body for the purpose of fighting certain infections. In people with allergies, however, IgE is made in response to non-infectious substances, such as foods, medications, or insect venoms. This IgE then sticks to the outside of mast cells and basophils, a type of white blood cell.

If a person with IgE antibodies to a specific allergen is exposed to that allergen again, the cells may suddenly become activated. The activated cells release large amounts of inflammation-causing chemicals (including histamine) into the blood stream, causing anaphylaxis.

The chemicals released from the cells cause the signs and symptoms typical of anaphylaxis. (See "Anaphylaxis symptoms" above). The allergic reaction can be so strong that it becomes life-threatening; for example, sudden severe swelling in the throat can lead to suffocation.

In some people with anaphylaxis, the reaction is caused by a process that does not involve allergens and IgE. However, the symptoms and treatment are the same.

ANAPHYLAXIS RISK FACTORS — Some people are more likely than others to experience anaphylaxis or to develop severe symptoms during anaphylaxis, for example, those who have one or more of the following: Previous sudden severe allergic reaction involving the whole body — People who have had allergic reactions to a particular substance in the past are at increased risk of anaphylaxis. However, the severity of past allergic reactions does not reliably predict the severity of future reactions; people with mild reactions in the past may experience severe anaphylactic reactions in the future. Asthma — People with asthma are more likely to have more severe respiratory problems during anaphylaxis. The combination of food allergy (especially to peanuts and tree nuts) and asthma seems to put people at risk for life-threatening episodes of anaphylaxis. Other diseases — People with chronic lung disease, especially older adults with chronic obstructive pulmonary disease (COPD) or emphysema, are at increased risk of complications during an anaphylactic reaction. People with coronary artery disease and other heart diseases are also at greater risk of developing complications during an anaphylactic reaction.

ANAPHYLAXIS DIAGNOSIS — The diagnosis of anaphylaxis is based upon symptoms that occur suddenly after being exposed to a potential trigger, such as a food, medication, or insect sting.

Is it anaphylaxis or another problem? — A number of other heath problems can cause symptoms that are similar to those of anaphylaxis. These include a severe asthma attack, a heart attack, a panic attack, or even food poisoning. Evaluation by a specialist can help to clarify the diagnosis.

Tryptase is a protein that is released into the blood during an anaphylactic reaction. An increased amount of tryptase can sometimes be measured in a blood sample collected during the first three hours after anaphylaxis symptoms have begun. Unfortunately, tryptase levels are normal in many people with anaphylactic reactions. For example, it is seldom elevated in food-induced anaphylaxis

Patient information: Allergy to penicillin and related antibiotics

PENICILLIN ALLERGY OVERVIEW — Serious allergies to penicillin are common, with about 10 percent of people reporting an allergy. However, about 90 percent of people who believe they are allergic can take penicillin without a problem, either because they were never truly allergic or because their allergy to penicillin diminished and resolved over time.

People who have a remote history of allergic reaction to a medication may become less allergic as time passes. Only about 20 percent of people will be allergic to penicillin 10 years after their initial allergic reaction if they are not exposed to it again during this time period.

WHAT IS PENICILLIN? — Penicillin is one of the most commonly prescribed antibiotics. It is part of a family of antibiotics known as beta lactams. Penicillins can be classified into the following categories: Penicillin G (also known as benzylpenicillin) Anti-staphylococcal penicillins (nafcillin, oxacillin, cloxacillin and dicloxacillin) Broad spectrum penicillins

- Second generation (ampicillin, amoxicillin and related agents)
- Third generation (carbenicillin and ticarcillin)
- Fourth generation (piperacillin)


Anyone who is allergic to one of the penicillins is allergic to all penicillins. One of the major differences among the penicillins is the range of bacteria against which they are active. Penicillin G and the anti-staphylococcal penicillins treat a small number of specific bacteria. On the other hand, the second, third, and fourth generation penicillins are capable of treating a wide range of bacteria, and are therefore called "broad spectrum".

REACTIONS TO PENICILLIN — A variety of unexpected reactions can occur after taking penicillin.

Adverse reactions — "Adverse reaction" is the medical term for any undesirable reaction caused by a medication. Allergic adverse reactions are less common than non-allergic adverse reactions. Stomach upset and diarrhea are examples of non-allergic adverse reactions.

It is important to distinguish non-allergic adverse reactions from true allergic reactions. Some people report that they are allergic to penicillin when actually they have had a non-allergic side effect. As a result, the person may be treated for a particular infection with a less-effective or more toxic antibiotic. This can lead to antibiotic failure or resistance, which can be costly and prolong illness.

When reporting past problems with antibiotics, it is important to provide as much detail as possible about the reaction. Anyone who is uncertain if a past allergic reaction was truly caused by allergy should avoid the antibiotic until they have discussed the situation with their healthcare provider.

Rashes — Several different types of rashes can appear while people are taking penicillin. Rashes that involve hives (raised, intensely itchy spots that come and go over hours, show picture 1) suggest a true allergy.

However, some people, especially young children, can develop flat, blotchy rashes that spread over days but do not change by the hour (show picture 2). These rashes typically start after several days of treatment. This type of rash is less likely to indicate a dangerous allergy, although it can be difficult to distinguish between different types of rashes that occurred in the past. Taking a photograph of a rash is always helpful.

Allergic reactions — An allergic reaction occurs when the immune system begins to recognize a drug as something "foreign". Several different symptoms can indicate that a person is allergic to penicillin. These include hives (raised, intensely itchy spots that come and go over hours) (show picture 1), angioedema (swelling of the tissue under the skin, commonly around the face), wheezing and coughing from asthma-like reactions (narrowing of the airways into the lungs).

A past history of these types of reactions is important because the person might develop a more severe reaction, such as anaphylaxis, if they were to take the antibiotic again. Mild to moderate allergic reactions to penicillins are common, occurring in 1 to 5 percent of people.

Anaphylaxis — Anaphylaxis is a sudden, potentially life-threatening allergic reaction. Symptoms include those of an allergic reaction, as well as very low blood pressure, difficulty breathing, abdominal pain, swelling of the throat or tongue, and/or diarrhea or vomiting. Fortunately, anaphylaxis is uncommon. (See "Patient information: Anaphylaxis symptoms and diagnosis").

PENICILLIN ALLERGY TESTING — In some situations, it is necessary to determine with certainty if a person is allergic to penicillin. Testing for allergy is recommended in the following situations: People who have a suspected penicillin (or closely related antibiotic) allergy and require penicillin to treat a life-threatening condition for which no alternate antibiotic is appropriate. People who have frequent infections but have suspected allergies to many antibiotics, leaving few options for treatment. Penicillin skin testing is suggested for anyone with a history of penicillin allergy (when penicillin skin test solutions become commercially available again). Because 90 percent of people will test negative, this type of evaluation can decrease medical costs and reduce the use of unnecessarily strong (ie, broad-spectrum) antibiotics.

Penicillin skin testing does not provide any information about certain types of reactions. This includes anyone who has experienced a severe reaction with extensive blistering and peeling of the skin (Stevens-Johnson syndrome or toxic epidermal necrolysis), a widespread sunburn-like reaction that later peeled (erythroderma), or a rash composed of small bulls-eyes or target-like spots (erythema multiforme),
People with these types of reactions should never again be given the medication that caused the reaction. This applies to all situations since a second exposure could cause a severe progressive reaction and even death.

Skin testing — Skin testing is the most reliable method to determine the risk of a serious, sudden onset allergic reaction in a person with a history of allergy to penicillin.

Several different types of penicillin preparations are required for skin testing. These preparations can be manufactured commercially but are not currently available in the United States. Thus, the most reliable type of skin testing for penicillin allergy cannot be performed in the United States at this time. It is expected that the preparations will be available again within the next 12 to 24 months.

Until skin tests are available, options for people who may be allergic to penicillin include: Take an different antibiotic Undergo a challenge test (See "Challenge testing" below) Undergo desensitization (See "Penicillin desensitization" below)

Skin testing procedure — Skin testing should be done by an allergist in an office or hospital setting. Testing usually takes less than one hour to complete. The skin is pricked with weak solutions of the various preparations of penicillin and observed for a reaction. This may cause discomfort due to itching, but it is not painful. If there is no skin reaction, slightly stronger solutions are then used.

A positive skin reaction is an itchy, red bump that lasts about half an hour and then resolves. The testing is stopped if a skin reaction occurs since this indicates that the person is truly allergic.

If the patient completes the skin testing without a positive reaction, a single oral dose of full strength penicillin is commonly given. This confirms that the patient does not have an allergy to the medication. The oral dose is given since there is a very small risk of false negative results (when the skin test is negative although the person is actually allergic).

Interpreting results — Medical tests, including skin testing, are rarely 100 percent accurate. Most people with a positive penicillin skin test will experience an allergic reaction if given penicillin or a related antibiotic (as would be expected). However, 3 percent or less of people with a history of penicillin allergy and a negative skin test will experience an allergic reaction. These reactions are always mild, and anaphylaxis in this situation is rare.

If a person has a negative skin test and has no reaction to an oral dose of the antibiotic, no future precautions are necessary.

Challenge testing — Because skin testing is not currently available in many places, a healthcare provider may recommend a challenge test. However, this is only recommended if the person requires penicillin, no other antibiotic is available, and the chances of a true allergy are small (eg, last reaction was at least 10 years ago or allergic reaction symptoms not likely caused by true allergy). If the chances of a true allergy are high, desensitization is generally recommended.

Challenge testing is usually done in an office setting, starting with a very small dose of the antibiotic given by mouth. If the person tolerates the smallest dose, a larger dose is given every 30 to 60 minutes until he/she has signs of an allergic reaction or the full dose is given. If the person tolerates the full dose, he or she is not allergic to the antibiotic.

PENICILLIN DESENSITIZATION — Desensitization can be done for people who are truly allergic to penicillin but require treatment with it or a closely related antibiotic. Desensitization refers to a process of giving a medication in a controlled and gradual manner, which allows the person to tolerate it temporarily without an allergic reaction.

Technique — Desensitization can be performed with oral or intravenous medications, but should always be performed by an allergy specialist. There are different techniques for desensitization. Some patients undergo desensitization in an outpatient clinic under supervision while others are treated in an intensive care unit.

Limitations — While usually successful, desensitization has two important limitations. Desensitization does not work and must never be attempted for certain types of reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis, erythroderma, and erythema multiforme). Desensitization also does not work for other types of immunologic reactions to antibiotics, such as serum sickness, drug fever, or hemolytic anemia. Desensitization is temporary. A person is unlikely to have an allergic reaction to the medication during treatment, after undergoing desensitization, as long as the antibiotic is taken regularly. However, once the antibiotic is stopped for more than 24 hours (times differ slightly for different medications), the person is again at risk for a sudden allergic reaction. Repeat desensitization is required if the same medication is needed again.

OTHER ANTIBIOTIC ALLERGIES — Reliable skin tests are not commercially available for some antibiotics. Thus, determining if a person has an allergy to these antibiotics is more difficult, and is mostly based on the history of the reaction. Skin testing with other antibiotics is sometimes performed, but the results are much less certain than those of penicillin testing.

Cephalosporins — Cephalosporins are a class of antibiotics closely related to penicillin. There are a number of cephalosporin medications available, a few of which include cephalexin (Keflex®), cefaclor (Ceclor®), cefuroxime (Ceftin®), cefadroxil (Duricef®) , cephradine (Velocef®). cefprozil (Cefzil®), loracarbef (Lorabid®), ceftibuten (Cedax®), cefdinir (Omnicef®), cefditoren (Spectracef®), cefpodoxime (Vantin®) and cefixime (Suprax®).

People with a history of penicillin allergy have a small risk of having an allergic reaction to cephalosporins. If possible, penicillin skin testing should be performed in these individuals. Since testing will be negative in about 90 percent of these people, a negative test will allow them to take cephalosporins safely. People with a positive skin test to penicillin have a small risk of an allergic reaction to cephalosporins and may require more caution in terms of how the cephalosporin is administered.

Allergic reactions to cephalosporins are less common than reactions to penicillin. In addition, skin testing to evaluate cephalosporin allergy is not as accurate as penicillin skin testing. If a cephalosporin is required, then there are several options: Take an different antibiotic Undergo a challenge test (See "Challenge testing" above) Undergo desensitization (See "Penicillin desensitization" above)

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Monday, August 2, 2010

Barbados Cherry

The Barbados cherry, a member of the Malpighiaceae, is an interesting example of a fruit that rose, like Cinderella, from relative obscurity about 40 years ago. It was at that time the subject of much taxonomic confusion, having been described and discussed previously under the binomial Malpighia glabra L., which properly belongs to a wild relative inhabiting the West Indies, tropical America and the lowlands of Mexico to southern Texas, and having smaller, pointed leaves, smaller flowers in peduncled umbels, styles nearly equal, and smaller fruits. M. Punicifolia L. (M. glabra Millsp. NOT Linn.) has been generally approved as the correct botanical name for the Barbados cherry, which is also called West Indian cherry, native cherry, garden cherry, French cherry; in Spanish, acerola, cereza, cereza colorada, cereza de la sabana, or grosella; in French, cerisier, cerise de St. Domingue; in Portuguese, cerejeira. The name in Venezuela is semeruco, or cemeruco; in the Netherlands Antilles, shimarucu; in the Philippines, malpi (an abbreviation of the generic name).

Barbados Cherry
Plate XXV: BARBADOS CHERRY, Malpighia punicifolia
Description

The Barbados cherry is a large, bushy shrub or small tree attaining up to 20 ft (6 m) in height and an equal breadth; with more or less erect or spreading and drooping, minutely hairy branches, and a short trunk to 4 in (10 cm) in diameter. Its evergreen leaves are elliptic, oblong, obovate, or narrowly oblanceolate, somewhat wavy, 3/4 to 2 3/4 in (2-7 cm) long, 3/8 to 1 5/8 in (9.5-40 mm) wide, obtuse or rounded at the apex, acute or cuneate at the base; bearing white, silky, irritating hairs when very young; hairless, dark green, and glossy when mature. The flowers, in sessile or short-peduncled cymes, have 5 pink or lavender, spoon-shaped, fringed petals. The fruits, borne singly or in 2's or 3's in the leaf axils, are oblate to round, cherry-like but more or less obviously 3-lobed; 1/2 to 1 in (1.25-2.5 cm) wide; bright-red, with thin, glossy skin and orange-colored, very juicy, acid to subacid, pulp. The 3 small, rounded seeds each have 2 large and 1 small fluted wings, thus forming what are generally conceived to be 3 triangular, yellowish, leathery-coated, corrugated inedible "stones".

Origin and Distribution

The Barbados cherry is native to the Lesser Antilles from St. Croix to Trinidad, also Curacao and Margarita and neighboring northern South America as far south as Brazil. It has become naturalized in Cuba, Jamaica and Puerto Rico after cultivation, and is commonly grown in dooryards in the Bahamas and Bermuda, and to some extent in Central and South America.

The plant is thought to have been first brought to Florida from Cuba by Pliny Reasoner because it appeared in the catalog of the Royal Palm Nursery for 1887-1888. It was carried abroad rather early for it is known to have borne fruit for the first time in the Philippines in 1916. In 1917, H.M. Curran brought seeds from Curacao to the United States Department of Agriculture. (S.P.I. #44458). The plant was casually grown in southern and central Florida until after World War II when it became more commonly planted. In Puerto Rico, just prior to that war, the Federal Soil Conservation Department planted Barbados cherry trees to control erosion on terraces at the Rio Piedras Experiment Station. During the war, 312 seedlings from the trees with the largest and most agreeably-flavored fruits were distributed to families to raise in their Victory Gardens. Later, several thousand trees were provided for planting in school yards to increase the vitamin intake of children, who are naturally partial to the fruits.

An explosion of interest occurred as a result of some food analyses being conducted at the School of Medicine, University of Puerto Rico, in Rio Piedras in 1945. The emblic (Emblica officinalis L.) was found to be extremely high in ascorbic acid. This inspired one of the laboratory assistants to bring in some Barbados cherries which the local people were accustomed to eating when they had colds. These fruits were found to contain far more ascorbic acid than the emblic, and, because of their attractiveness and superior eating quality, interest quickly switched from the emblic to the Barbados cherry. Much publicity ensued, featuring the fruit under the Puerto Rican name of acerola. A plantation of 400 trees was established at Rio Piedras in 1947 and, from 1951 to 1953, 238 trees were set out at the Isabela Substation. By 1954, there were 30,000 trees in commercial groves on the island. Several plantings had been made in Florida and a 2,000-acre (833-ha) plantation in Hawaii. There was a great flurry of activity. Horticulturists were busy making selections of high-ascorbic-acid clones and improving methods of vegetative propagation, and agronomists were studying the effects of cultural practices. Smaller plantings were being developed in Jamaica, Venezuela, Guatemala, Ghana, India, the Philippines and Queensland, Australia, and even in Israel. Many so-called "natural food" outlets promoted various "vitamin C" products from the fruits–powder, tablets, capsules, juice, sirup.

At length, enthusiasm subsided when it was realized that a fruit could not become a superstar because of its ascorbic acid content alone; that ascorbic acid from a natural source could not economically compete with the much cheaper synthetic product, inasmuch as research proved that the ascorbic acid of the Barbados cherry is metabolized in a manner identical to the assimilation of crystalline ascorbic acid.

The large plantation of the Hawaiian Acerola Company (a subsidiary of Nutrilite Products Company) was abandoned for this reason, and low fruit yields; and, so it is said, the low ascorbic acid content because of the high copper levels in the soil. Puerto Rican production was directed thereafter mainly to the use of the fruit in specialty baby foods.

Frozen fruits are shipped to the United States for processing.

Varieties

In 1956, workers at the University of Florida's Agricultural Research and Education Center in Homestead, after making preliminary evaluations and selections, chose as superior and named the 'Florida Sweet', a clone that was observed to have an upright habit of growth, large fruits, thick skin, apple-like, semi-sweet flavor, and high yield.

The first promising selections in Puerto Rico, on the bases of fruit size, yield and vitamin content, were identified as 'A-l' and 'B-17', but these were later found to be inferior to 'B-15' in ascorbic acid level and productivity. Yields of 10 clones ('A-l', 'A-2', 'A-4', 'A-10', 'A-21', 'B-2', 'B-9', 'B-15', 'B-17', and 'K-7') were compared over a 2-year period (1955-56) in Puerto Rico and 'B-15' far exceeded the others in both years.

A horticultural variety in St. Croix, formerly known as M. thompsonii Britton & Small, has displayed unusually large leaves and fruits and more abundant flowers than the common strain of Barbados cherry.

Climate

The Barbados cherry can be classed as tropical and subtropical, for mature trees can survive brief exposure to 28º F (-2.22º C). Young plants are killed by any drop below 30º F (-1.11º C). It is naturally adapted to both medium- and low-rainfall regions; can tolerate long periods of drought, though it may not fruit until the coming of rain.

Soil

The tree does well on limestone, marl and clay, as long as they are well drained. The pH should be at least 5.5. Elevation to 6.5 significantly improves root development. Acid soils require the addition of lime to avoid calcium deficiency and increase yield. The lime should be worked into the soil to a depth of 8 in (20 cm) or more.

Propagation

If seeds are used for planting, they should be selected from desirable clones not exposed to cross-pollination by inferior types. They should be cleaned, dried, and dusted with a fungicide. It should also be realized that the seeds in an individual fruit develop unevenly and only those that are fully developed when the fruit is ripe will germinate satisfactorily. Germination rates may be only 50% or as low as 5%. Seedlings should be transferred from flats to containers when 2 to 3 in (5-7.5 cm) high.

Air-layering (in summer) and side-veneer, cleft, or modified crown grafting are feasible but not popular because it is so much easier to raise the tree from cuttings. Cuttings of branches 1/4 to 1/2 in (6-12.5 mm) thick and 8 to 10 in (20-25 cm) long, with 2 or 3 leaves attached, hormone-treated and set in sand or other suitable media under constant or intermittent mist, will root in 60 days. They are then transplanted to nursery rows or containers and held in shade for 6 months or a year before being set out in the field. Some fruits will be borne a year after planting but a good crop cannot be expected until the 3rd or 4th year. The tree will continue bearing well for about 15 years. There is a lapse of only 22 days between flowering and complete fruit maturity.

Grafting is generally practiced only when cuttings of a desired clone are scarce or if a nematode-resistant rootstock is available on which to graft a preferred cultivar; or when top-working a tree that bears fruits of low quality.

Culture

The Barbados cherry tree will grow and fruit fairly well with little care. For best performance, Puerto Rican agronomists have recommended a fertilizer formula of 8-8-13 twice annually for the first 4 years at the rate of 1/2 to 1 lb (0.22-0.45 kg). Older trees should have 3 to 5 lbs (1.35-2.25 kg) per tree. In addition, organic material should be worked into the planting hole and also supplied in amounts of 10 to 20 lbs (4.5-9 kg) per tree. Under Florida conditions, a 10-10-10 formula is given in February, 1 lb (0.22 kg) for each year of growth. In May, July and September, a 4-7-5-3 formula is recommended, 1 lb (0.22 kg) for each year of age up to the 10th year. Thereafter, a 6-4-6-3 mixture is given–5 lbs (2.25 kg) per tree in late winter and 10 lbs (4.5 kg) per tree for each of the summer feedings. On limestone soils, sprays of minor elements–copper, zinc, and sometimes manganese–will enhance growth and productivity. Young trees need regular irrigation until well established; older trees require watering only during droughts. Mature plants will bear better if thinned out by judicious pruning after the late crop and then fertilized once more.

Pollination and Fruit Set

In Florida, bees visit Barbados cherry flowers in great numbers and are the principal pollinators. Maintenance of hives near Barbados cherry trees substantially improves fruit set. In Hawaii, there was found to be very little transport of pollen by wind, and insect pollination is inadequate. Consequently, fruits are often seedless. Investigations have shown that growth regulators (IBA at 100 ppm; PCA at 50 ppm) induce much higher fruit set but these chemicals may be too costly to buy and apply.

Season

In Florida, the Bahamas, Puerto Rico and Hawaii the fruiting season varies with the weather. There may be a spring crop ripening in May and then successive small crops off and on until December, but sometimes, if spring rains are lacking, there may be no fruits at all until December and then a heavy crop. In Zanzibar, the bearing season is said to be just the months of December and January.

Harvesting

For home use, as dessert, the fruits are picked when fully ripe. For processing or preserving, they can be harvested when slightly immature, when they are turning from yellow to red. As there is continuous fruiting over long periods, picking is done every day, every other day, or every 3 days to avoid loss by falling.

The fruits are usually picked manually in the cool of the early morning, and must be handled with care. For immediate processing, some growers shake the tree and allow the ripe fruits to fall onto sheets spread on the ground. Harvested fruits should be kept in the shade until transferred from the field, which ought to be done within 3 hours, and collecting lugs are best covered with heavy canvas to retard loss of ascorbic acid.

Yield

There is great variation in productivity. Individual trees may yield 30 to 62 lbs (13.5-28 kg) in Puerto Rico. In Jamaica, maximum yield in the 6th year is about 80 lbs (36 kg) per tree; 24,000 lbs/acre (24,000 kg/ha). Venezuelan growers have reported 10 to 15 tons/ha; the average in Puerto Rico is 25 tons/ha/yr. 'Florida Sweet' in Florida has yielded 65 tons/ha. A plot of 300 trees of 'Florida Sweet' has borne crops of 6,300 to 51,300 lbs (2,858-23,270 kg) of fruit from March to November, in Homestead, Florida.

In Puerto Rico, a planting of 200 trees may be expected to produce 3,600 to 5,400 lbs (1,636-2,455 kg) of juice. From the juice there can be extracted at least 120 lbs (54.5 kg) of vitamin C expressed as dehydroascorbic and ascorbic acid, providing the content is determined to be 2%. In Puerto Rico, it is calculated that 10 tons of fruit should yield 435 lbs (197 kg) ascorbic acid. In a commercial operation using ion-exchange resins, the yield of ascorbic acid from Barbados cherry juice is expected to be about 88%.

Keeping Quality

Ripe Barbados cherries bruise easily and are highly perishable. Processors store them for no more than 3 days at 45º F (7.22º C). Half-ripe fruits can be maintained for a few more days. If longer storage is necessary, the fruits must be frozen and kept at 10º F (-12.22º C) and later thawed for use. At one time it was believed that the fruits could be transported to processing plants in water tanks (as is done with true cherries) but it was discovered that they lose their color and ascorbic acid content in water.

At room temperature–85º F (29.44º C) in Puerto Rico–canned Barbados cherries and also the juice lose color and fresh flavor and 53% to 80% of their ascorbic acid content in one month, and metal cans swell because of the development of CO2. Refrigeration at 44.6º F (7º C) considerably reduces such deterioration. Juice in the home refrigerator will lose 20% of its ascorbic acid in 18 days. Therefore, the juice and the puree should be kept no longer than one week.

Pests and Diseases

One of the major obstacles to successful cultivation of the Barbados cherry is the tree's susceptibility to the root-knot nematode, Meloidogyne incognita var. acrita, especially in sandy acid soils. Soil fumigation, mulching and regular irrigation will help to keep this problem under control. The burrowing nematode, Radopholus similis, is also a cause of decline in otherwise healthy trees.

In Florida, the foliage is attacked by wax scale, Florida mango scale, and other scale insects, whiteflies, a leaf roller, and aphids. In Guatemala, the aphid, Aphis spiraecola, attacks the leaves and young, tender branches. This pest and the Hesperid caterpillar, Ephyriades arcas, require chemical control. In Puerto Rico, the tree is often damaged by the blue chrysomelid of acerola, Leucocera laevicollis. Some fruits may be malformed but not otherwise affected by the sting of stinkbugs. None of these predators is of any great importance.

The major pest in Florida is the Caribbean fruit fly, Anastrepha suspensa, which seems to attack all but very sour fruits and the larvae are commonly found inside. In Guatemala, a fruit worm, Anthonomus florus, deposits its eggs in the floral ovary and also in the fruits; the larvae feed in the fruits causing deformity and total ruin. Drastic control measures have been employed against this predator, including the incineration of all fallen, infested fruits and the elimination of all related species that serve as hosts.

Few diseases have been reported. However, in Florida, there are cases of anthracnose caused by Colletotrichum gloeosporioides, and leafspotting by the fungus, Cercospora bunchosiae, is a serious malady in Florida, Puerto Rico and Hawaii. Green scurf, identified with the alga, Cephaleuros virescens, occurs in Puerto Rico.

Food Uses

Barbados cherries are eaten out-of-hand, mainly by children. For dessert use, they are delicious merely stewed with whatever amount of sugar is desired to modify the acidity of the particular type available. The seeds must be separated from the pulp in the mouth and returned by spoon to the dish. Many may feel that the nuisance is compensated for by the pleasure of enjoying the flavorful pulp and juice. Other-wise, the cooked fruits must be strained to remove the seeds and the resulting sauce or puree can be utilized as a topping on cake, pudding, ice cream or sliced bananas, or used in other culinary products. Commercially prepared puree may be dried or frozen for future use. The fresh juice will prevent darkening of bananas sliced for fruit cups or salads. It can be used for gelatin desserts, punch or sherbet, and has been added as an ascorbic acid supplement to other fruit juices. The juice was dried and powdered commercially in Puerto Rico for a decade until the cost of production caused the factory to be closed down.

The fruits may be made into sirup or, with added pectin, excellent jelly, jam, and other preserves. Cooking causes the bright-red color to change to brownish-red. The pasteurization process in the canning of the juice changes the color to orange-red or yellow, and packing in tin cans brings on further color deterioration. Enamel-lined cans preserve the color better.

Wine made from Barbados cherries in Hawaii was found to retain 60% of the ascorbic acid.

Food Value Per 100 g of Edible Portion*
Calories 59
Moisture 81.9-91.10 g
Protein 0.68-1.8 g
Ether Extract 0.19-0.09 g
Fiber 0.60-1.2 g
Fat 0.18-0.1 g
Carbohydrates 6.98-14.0 g
Ash 0.77-0.82 g
Calcium 8.2-34.6 mg
Phosphorus 16.2-37.5 mg
Iron 0.17-1.11 mg
Carotene 0.003-0.408 mg
(Vitamin A) 408-1000 I.U.
Thiamine 0.024-0.040 mg
Riboflavin 0.038-0.079 mg
Niacin 0.34-0.526 mg
Ascorbic Acid**

*According to analyses made in Hawaii, Guatemala, and elsewhere.

**According to analyses at the Massachusetts Institute of Technology of fruits grown in Barbados: 4,500 mg (green), 3,300 mg (medium-ripe), 2,000 mg (very ripe). The ascorbic acid level of unripe fruits can range up to 4,676 mg and such ratings are exceeded only by the fruits (rose hips) of Rosa rugosa Thunb., which may have as much as 6,977 mg/100 g. This constituent varies as much as 25% with the clone, the locale, cultural methods and degree of exposure to sunlight during developmental stages and after harvesting. At INCAP (Instituto de Nutricion de Central America and Panama), in Guatemala assays in 1950-1955 showed distressingly low levels–an average of 17 mg/100 g, whereas fruits sent to INCAP by air and in dry ice from Florida were analyzed and contained 1,420 mg/100 g. In field experiments, treatment of young fruits on the tree with 200 ppm gibberellic acid has brought about a marked increase in the ascorbic acid content of the mature fruits.

The ascorbic acid is not totally destroyed by heat, for the jelly may contain 499-1,900 mg/100 g. Of the total ascorbic acid in Barbados cherry juice, 0.18% is in the bound form. Other constituents include dextrose, levulose, and a little sucrose.

Harmful Effects

Physicians in Curacao report that children often require treatment for intestinal inflammation and obstruction caused by eating quantities of the entire fruits, including seeds, from the wild Barbados cherries which abound on the island.

People who pick Barbados cherries without gloves and long sleeves may suffer skin irritation from contact with the minute stinging hairs on the leaves and petioles.

Other Uses

Bark: The bark of the tree contains 20-25% tannin and has been utilized in the leather industry.

Wood: The wood is surprisingly hard and heavy. Trials have demonstrated that it refuses to ignite even when treated with flammable fluid unless perfectly dry.

Medicinal Uses: The fruits are considered beneficial to patients with liver ailments, diarrhea and dysentery, as well as those with coughs or colds. The juice may be gargled to relieve sore throat.

Black sugar maple

Hard maple

A. nigrum Michx. f.

Source: Magness et al. 1971

Maple sugar and syrup are obtained from the sap of these two species and are solely products of the United States and Canada. The Indians were making crude syrups and sugar from maple sap before the coming of white men. The preparation of maple sugar and syrup is strictly a farm industry, occurring from Kentucky northwest to Iowa, northeast to Maine and north into Canada. Native stands of these maple species are tapped to obtain the dilute juice or sap. The trees are not a cultivated crop, although competing useless trees may be removed and maple stands may be thinned to promote better growth and sugar yield. Only a small proportion of the available trees of these species are actually tapped. It is estimated that more than 200 million such trees are growing in the United States, and less than 6 million are tapped.

The tapping is done by boring a small hole (under 0.5-inch diameter) horizontally into the tree so as to penetrate through the outer or sap wood. On large trees up to four such taps may be made at one time. Tapered spouts (hollow tubes) are driven into the holes to fit tightly, and the sap flows through this tube and is collected in sap buckets. it is important to protect the buckets and contents from rain water. Tapping is done in late winter, before bud break. During periods when temperatures are above freezing at this season sap flow is quite abundant, A tap hole usuallv produces 5 to 15 gallons of sap, though much more than that is sometimes obtained. Sugar content of the sap also varies widelv, from l0 to 30°Brix or higher.

Portable tanks of various types are used to collect the sap, which is poured into the tank through strainers. An alternative method is to use pipc lines to carry the sap to the evaporation equipment.

Originally a single open kettle over a fire was used to evaporate the excess water in the sap to produce syrup. Now multiple evaporators are mainly used, the syrup being transferred as it becomes more dense. Usually 2 or 3 transfers are made. Modem evaporating pans have flues in them through which the heat from the fuel passes to speed the process and codserve fuel. For standard-density syrup, concentration is to 65.5°Brix, which is about 86 percent solids by weight. If the sap tests 2.4°Brix, 34 gallons would be required to produce one gallon of syrup.

Slow evaporation--or longer heating time--in the final stages of concentration result in a darker colored syrup. More rapid evaporation at this stage gives a lighter colored, higher grade syrup. Sensitive thermometers are used to determine when the syrup is concentrated to the standard of 65.5 Brix. The completed syrup contains solid granules, mainly calcium malate, termed sugar sand. For toable syrup these must be removed. On the farm they may be allowed to settle out or are removed by filtering. Centrifuging is efficient if available.

To produce various types of maple sugar, the syrup is further heated and additional water driven off. If heated to a boiling point of 230°F. and cooled rapidly without stirring a solid cake is formed. Stirring during cooling results in crystal formation. For fine crystals the highly supersaturated solution is seeded with fine crystals and stirred rapidly, which results in rapid formation of great numbers of fine crystals.

Numerous products, as maple cream, or butters, soft-sugar candies, maple spread, and candies utilize maple syrup or sugar. Total maple syrup production in the United States averaged approximately 1,400,000 gallons, 1961-66, inclusive. This includes that made into sugar. In addition about 800,000 gallons of syrup and 5,145,000 pounds of sugar were imported annually from Canada during those years.

Cucurbit Resources in Namibia

Namibia has several cucurbits with potential for development into commercial crops either through selection or through the introduction of genes into known crops. Acanthosicyos horrida Welw. ex J.D. Hook., wild Citrullus ecirrhosus Cogn., and C. lanatus (Thunb.) Matsum. & Nakai in the Cucurbitaceae are examples of gene sources. The areas from which these plants come are arid and the plants derive their water needs from dew precipitation in the mornings, very occasional rains every few years, and deep ground water (Seely l987; Lovegrove 1993).

ACANTHOSICYOS HORRIDA

Acanthosicyos horrida forms clumps of vegetation in the dunes of the Sossuvlei region near Walvis Bay (Fig. 1) (Craven and Marais 1986; Lovegrove 1993; Klopatek and Stock 1994). Acanthosicyos horrida is a dioecious perennial cucurbit attaining a height of about 1.5 m (Fig. 2). It forms plants of one sex in single clumps which may touch plants of the same or other sex nearby (Fig. l). It bears deep water table seeking roots (G. Wardell–Johnson, pers. commun. 1998). The plants are totally leafless (Fig. 2) and have a fruiting habit of oblong spherical fruits reaching up to 25 cm average diameter. The plants are able to build up sand deposits around themselves and continuously grow to be above these sand deposits. New plants establish only when rain falls and quickly form deeply growing roots that seek the water table (G. Wardell–Johnson, pers. commun. 1998).

Figure 1 Figure 2
Fig. 1. View of Acanthosicyos horrida in sand dunes at the Sossuvlei region near Walvis Bay Namibia. Fig. 2. A close up of Acanthosicyos horrida plants. Note the leaflessness.

The fruit may not be spaced apart and may occur in clusters of several touching each other. The fruits are spiny (Fig. 3). Maturation of the fruits occurs between February and April. The fruits do not change color and remain green on the outside but the flesh surrounding the seeds dissociates from the skin, turns orange in color (Fig. 4), extremely sweet in taste and strongly aromatic. Maturational changes are easily detected by the bushmen living in the area without breaking the fruit in any way. The fruits are used by the bushmen for two main purposes. The first is for the extraction of the seed which are consumed as pips by splitting in the mouth and the second is for pulp processing where the flesh is boiled and poured to form a fruit leather. This fruit leather is eaten throughout the year and is considerably less flavorful than the pulp. The plant thus forms an important food resource because of the easy storage of both the seeds and the dried pulp (leather). The fruits are eaten also when immature by animals including jackals and rodents who do not seem to be bothered by the bitter taste of the fruits caused by cucurbitacins (Hylands and Magd 1986).

Figure 3 Figure 4
Fig. 3. Back of a mature fruit of Acanthosicyos horrida showing the large spines on the surface of the fruit. The distances separating the spines are small in young fruits. Fig. 4. Cross section through three fruits of Acanthosicyos horrida. The one on the extreme right is a bitter immature fruit of full size. The one on the top an almost mature fruit with only a little bitterness. The bottom left hand fruit a fully mature fruit with a flesh having an orange color, no bitterness and very aromatic in flavor.

The mature pulp has a flavor which is aromatic and maybe due in part to sulphur components as in some types of Cucumis melo L. No trace can be tasted of cucurbitacins in the mature pulp. The pulp could be commercialized and used to make ice-cream, and could be freeze dried and chocolate coated. The seeds which are already sold to an European population in Walvis Bay can have their market expanded by selling the seeds either whole or dehusked in packaging developed for nuts. Their rarity should provide a premium price and help the economic existence of the bushmen in this area. Ice-cream manufacture and freeze drying facilities are only within 30 km of the bushmen. Partnerships with firms interested in commericalizing the unique, aromatic pulp of Acanthosicyos horrida could be fostered to further improve the economic existence of the native people in the area.

CITRULLUS ECIRRHOSUS

Citrullus ecirrhosus is a desert perennial (Fig. 5, 6) which is monoecious. Fruits mature (Fig. 7, 8) February to March. The leaves form an annual stems which die back each year. The leaves have a special feature where the lamina is curved over the mid-rib and the lateral veins so that when viewed from above the top surface is only visible in the vein regions and the leaves have a greenish white appearance due to the lower epidermis being reflected up as the upper surface of the leaf. This lower epidermis is covered with warts and hairs which account for the whitening effect. Both lower and upper epidermis contain similar amounts of stomata. The water relations of this plant are reliant on a deep water layer in the ground which the roots reach and possibly some water availability from morning fogs and the very occasional rainfall. The fruit and seeds contain cucurbitacins but the seeds are harvested in times of need and processed by crushing and decantation to remove the bitter substances. Citrulls ecirrhosus plants may be a source of drought tolerance genes for Citrulls lanatus. Successful crossability of Citrulls ecirrhosus and C. lanatus is discussed in Navot and Zamir (1986) and Navot et al. (1990). They have shown the way for breeding Citrullus lanatus containing genes from C. ecirrhosus.

Figure 5 Figure 6
Fig. 5. Citrullus ecirrhosus perennial plant growing approximately 20 km inland from Walvis Bay, showing a mature fruit on current years growth and brown dead stems from last years growth. Fig. 6. Citrullus ecirrhosus perennial plant showing young developing fruit in the foreground and the bending of the leaves over the mid-rib and lateral veins.
Figure 7 Figure 8
Fig. 7. Mature Citrullus ecirrhosus showing folded nature of the leaves of the mid-rib and lateral veins. Fig. 8. Fruit of Citrullus ecirrhosus cut showing white creamy flesh which is non juicy and brown seeds.

Figure 9
Fig. 9. Citrullus lanatus mature fruit from a plant growing on a dry river bed approximately 20 km inland from Walvis Bay, cut to show chlorophyll in the flesh and browny-black seeds. The more deeply colored regions of the flesh are green. The flesh is more juicy than in Citrullus ecirrhosus.

CITRULLUS LANATUS

Citrullus lanatus wild plants seen near Walvis Bay have green fleshed fruit unknown from domesticated watermelons (Fig. 9). The genetics of fruit color in the watermelon, Citrullus colocynthis and ecirrhosus are discussed by Navot et al. (1990). White, yellow, orange, pink, red, and crimson flesh types are known. The green flesh color of this wild Citrullus lanatus (Fig. 9) is a unique feature which can be transferred to domestic watermelon due to the crossability of wild and domestic watermelons. This would offer a new fruit type for consumers to enjoy. A red flesh cultivated watermelon from the north of Namibia has some green zone within the fruit suggesting that the green flesh character can be easily introduced. However, the wild watermelon has cucurbitacins which would render them unfit for human consumption. Drought tolerance and green flesh color from C. ecirrhosus and wild Citrullus lanatus, could be valiable traits for watermelon improvement.

REFERENCES

  • Craven, P. and C. Marais. 1986. Namib Flora Swakopmund to the Giant Welwitschia via Goanikontes. Gamsberg MacMillan Publishers: Windhoek. p. 80–83.

  • Hylands, P.J and M.S. Magd. 1986. Cucurbitacins from Acanthosicyos horridus. Phytochemistry 25:1681–1684.

  • Klopatek J.M. and W.D. Stock. 1994. Partitioning of nutrients in Acanthosicyos horrida, a keystone endemic species in the Namib Desert. J. Arid Environments 26:233–240.

  • Lovegrove, B. 1993. The living deserts of Southern Africa. Fernwood Press, Vlaeberg, South Africa. p. 30, 47, 71, 158, 190.

  • Navot, N. and D. Zamir. 1987. Isozyme and seed protein phylogeny of the genus Citrullus (Cucurbitaceae). Plant Syst. Evol. 156:61–68.

  • Navot, N., M. Sarfatti, and D. Zamir. 1990. Linkage relationships of genes affecting bitterness and flesh colour in watermelon. J. Hered. 81:162–165.

  • Seely, M. 1986. The Namib. Shell Namibia: Namibia. 2nd ed. 19, 43–45, 50, 84, 90.

Acacia seyal Del.

Uses

According to some Biblical scholars, the Shittah tree is mentioned in the Bible only once (I will plant in the wilderness... the Shittah tree. Isaiah 41), but its wood is referred to many times as shittium, which is the plural of shittah in Hebrew. Some even speculate that it was only natural that Moses should turn to shittium when he came to build the Ark of the Covenant and the Tabernacle and needed beams and timber. No one can really be sure which species of Acacia was meant. Wood is white to yellow-brown, finely-striated with dark lines, coarse-grained, soft, easy to work, polishes well, but discolors eastly with mold and is susceptible to insect attack. Ancient Egyptians made coffins, some still intact, from the wood. Nigerians used sapling stems, or also the roots for spear shafts. Tree also yields a gum of good quality, inferior to that of A. senegal. Systematic tapping has produced a product of better color and taste. Bark contains tannin and yields a red liquid extract. The gum is said to be edible. The leaves are important for forage and the wood for fuel where the trees are abundant. In parts of Africa the tree is important for livestock, natives driving their animals to where it is common and lopping off branches for them, both leaves and young pods being eaten. The pods are sold, especially for fattening sheep. The tree is believed to provide the best firewood in Chad, and the best fodder in Sahelian savannas (NAS, 1980a; Duke, 1983a).

Folk Medicine

The gum is believed to be aphrodisiac. The bark decoction Is used for dysentery and leprosy. Tanganyikans use the bark as a stimulant in tropical Africa. The gum is used as emollient and astringent for colds, diarrhea, hemorrhage and ophhthalmia. Mixed with Acacia sieberana DC, it is used for intestinal ailments on the Ivory Coast. Wood used as a fumigant for rheumatic pains, and to protect puerperal mothers from colds and fevers. Eating the gum is supposed to afford some protection against bronchitis and rheumatism (Duke, 1983a).

Chemistry

This species has been reported to contain 18–20% tannin.

Description

Tree 3–12 m tall, crown flat-topped; bark powdery, white to greenish-yellow or orange-red; sparsely branched, the branches horizontal or ascending; young branchlets with sparse hairs or almost glabrous, with numerous reddish sessile glands; epidermis of twigs becoming reddish and shed annually; leaves often with a large gland on petiole and between the top 1–2 pairs of pinnae; stipules spinescent, up to 8 cm long, ant-galls present or absent; pinnae usually 3–7 pairs, the leaflets in 11–20 pairs, 3–8 cm long, 0.75–1 mm wide, sparingly ciliolate or glabrous; lateral veins invisible beneath; flowers bright yellow, in axillary, pedunculate heads 10–13 mm across, borne on terminal or short lateral shoots of current season; involucel in lower half of peduncle 2–4 mm long; apex of bracteoles rounded to elliptic, sometimes pointed; calyx 2–2.5 mm long, puberulous in upper part; corolla 3.5–4 mm long, glabrous outside; pods 7–20 cm long, 0.5–0.9 cm in diameter, dehiscent, falcate, constricted between seeds, glabrous except for sessile glands, 6–9-seeded; seeds elliptic, 7–9 mm long, 4.5–5 mm wide, compressed, minutely wrinkled, olive-brown to olive; areole 5–6 mm long, 2.5–3.5 mm wide.

Germplasm

Species has several botanical varieties. The two main ones are: A. seyal var. fistula (Schweinf.) Oliv. (A. fistula Schweinf.), is white-barked with some pairs of spines fused at base into 'ant-galls', 0.8–3 cm in diameter, grayish or whitish, often marked with sienna-red and with longitudinal furrows down center, more or less 2-lobed. Found in Zambia, Malawi, and Mozambique. A. seyal var. multijuga Schweinf. ex Baker f. (A. stenocarpa Oliv., pro partem), a shrub or tree, usually less than 5 m tall, sometimes up to 13 m, flattened crown; bark on main stem greenish-brown, peeling in papery rolls; bark on branchlets red-brown, thorns straight, weak, usually less than 2.5 cm long, sometimes absent; pinnae 4–12 pairs, leaflets 10–20 pairs; flowers golden-yellow; pod narrow-linear, strongly curved, up to 10 cm long, 0.6 cm wide, dehiscing on tree. Common in overgrazed pastures and widely distributed in East Africa. Hybrids, A. seyal var. fistula X A. xanthophloea Benth., are known from woodlands on black clay loams on flood plains in Malawi. Pods are conspicuously irregular, 4–11 cm long, 6–10 mm wide, ill-formed and curved. Assigned to the Africa Center of Diversity, shittim wood or cultivars thereof is reported to exhibit tolerance to high pH, heavy soil, insects, mycobacteria, poor soil, salt, savanna, slope, and waterlogging. (2n= 26.)

Distribution

Native to the Sahelian Zone from Senegal to Sudan, it also occurs in Egypt and eastern and southern Africa, from Somalia to Mozambique and Namibia (NAS, 1980a).

Ecology

Trees thrive in Sclerocarya caffra woodlands, wooded grasslands and especially on seasonally flooded black-cotton soils along water courses. Requires a heavy clay-alluvium, but will grow on stony ground at base of hills. Grows at 20–2,100 m altitude. A gregarious savanna tree, ranging from Subtropical Desert to Dry through Tropical Desert to Very Dry Forest Life Zones, shittim wood is reported to tolerate annual precipitation of 8.7–22.8 dm (mean of 7 cases = 15.0 dm), annual mean temperature of 18.7–27.8°C (mean of 7 cases = 24.0°C) and pH of 5.0–8.0 (mean of 5 cases = 6.9).

Cultivation

Propagated from scarified seed. large cuttings are said to strike root readity in moist soils.

Harvesting

Pods, bark or wood are harvested in season from trees or shrubs in native habitats. Gum also obtained from native plantings, in manner similar to that for other gum arabic plants.

Yields and Economics

Gum and other products of some local importance in East Africa, but do not enter international trade.

Energy

The dense wood is highly prized for firewood, in areas where few other plants survive. Considered one of the best firewoods in Chad, it is used in the Sudan to make fragrant fires over which women perfume themselves.

Biotic Factors

Following fungi reported on this plant: Fomes rimosus, Ganoderma lucidum, Leveillula taurica, Ravenelia volkensii, Trametes meyenii, and Uromyces schweinfurthii. Although the plant is reportedly resistant to insect attacks, felled logs may be severely damaged by wood borers.

References

  • Duke, J.A. 1983a. Medicinal plants of the Bible. Trado-Medic Books, Owerri, NY.
  • N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.

Acacia tortilis (Forsk.) Hayne

Syn.: Acacia raddiana Savi,
Acacia spirocarpa Hochst. ex A. Rich
Acacia heteracantha Burch.
Mimosaceae
Umbrella Thorn, Israeli Babool

Source: James A। Duke. 1983. Handbook of Energy Crops. unpublished.

Uses

Since this is one of the few timber species of the Arabian deserts, it is suspected as being the wood from which the Biblical Ark of the Tabernacle was made. Kaplan (1979) says rather emphatically it is the Shittim of the Bible, which provided the Israelites with the large-size timbers for the Ark. The timber is also used for fenceposts, firewood, furniture, and wagonwheels. The prolific pods made good fodder for desert grazers and the foliage is also palatable, being one of the major dry season fodder trees for the Sahara-Sahelian belt. Bark, used for string in Tanganyika. Gum used as a poor man's gum arabic, said to be edible. It is the tree most recommended for reclaiming dunes in India and Africa (Roy et al, 1973). The thorny branches are used to erect temporary cages and pens. Bark said to be a good source of tannin (Roy et al, 1973). Africans once strung the pods into necklaces. Senegalese use the roots for spear shafts, Lake Chad natives use the stems for fish spears. African nomads often use the flexible roots for frameworks of their temporary shelters.

Folk Medicine

While I find few data specific to this species, I suspect that the gum is used like that of gum arabics in folk remedies. In French Guinea, the bark is used as a vermifuge and dusted onto skin ailments (Dalziel, 1937).

Chemistry

Pods contain close to 19% protein (Palmer and Pitman, 1972). NAS (1979) reports unconfirmed allegations that the foliage can be toxic to livestock. Certainly HCN has been reported in several Acacias. The following tables are reproduced, with permission, from FAO's Tropical Feeds (1981):

Nutritive tables (Gohl, 1981)



As % of dry matter

DM CP CF Ash EE NFE Ca P Ref.
Fresh leaves, South Africa
19.2 11.6 8.7 6.1 54.4 2.27 0.17 213
Pods, South Africa
17.3 24.8 5.7 3.1 49.1 0.79 0.34 213
Seeds, South Africa
37.8 10.9 5.9 6.0 39.7 0.56 0.73 213
Pod husks, South Africa
8.7 34.3 6.2 1.6 49.2 1.10 0.14 213
Acacia tortilis (Forsk.) Hayne subsp. heteracantha (Burch.) Brenan


As % of dry matter

DM CP CF Ash EE NFE Ca P Ref.
Fresh leaves, Sudan 90.9 13.3 9.4 9.6 8.3 59.4 4.00 0.15 64
Pods, Tanzania
12.3 22.4 5.6 1.8 57.9 0.98 0.24 166
Pods, Kenya
17.8 17.5 8.4 1.7 54.6 1.34 0.36 129


Digestibility (%)

Animal CP CF EE NFE ME Ref
Pods Cattle 46.2 42.0 74.0 76.6 2.30 166
Acacia tortilis (Forsk.) Hayne subsp. spirocarpa (Hochst. ex A. Rich) Brenan

Description

Medium umbrella-shaped tree 4–15 m tall, often with several trunks, reduced to a small wiry shrub less than 1 m tall under extremely arid conditions. Two types of thorns abound (1) long, straight, and white, and (2) small, hooked, and brownish. Leaves up to 2.5 cm long with 4–10 pairs of pinnae, each with ca 15 pairs of minute leaflets. Flowers white, aromatic, in small clusters. Pods flat, glabrose, coiled into a spring-like array.

Germplasm

Reported from North African and Middle Eastern Centers of Diversity, Umbrella Thorn, or cvs thereof, is reported to tolerate alkalinity, drought, heat, sand, slope, and stony soils. It seems to be more frost tolerant than Prosopis juliflora, still plants less than 2 years old are easily damaged by frost. Four subspecies are known in different ecological zones: subspecies tortilis—Sahel, Middle East; subspecies raddiana—Sudan, Middle East, Sahel(2n=104); subspecies spirocarpa—Eastern Africa, Sudan; and subspecies heteracantha—Southern Africa (2n= 52). The different subspecies seem to have different ecological tolerances, which is important to consider when choosing a subspecies for plantations. (2n= 52, 104)

Distribution

Native to much of Africa and the Middle East, this species has been introduced in many arid parts of the world. Ironically, it grows faster in the Rajastan Desert of India, where used for charcoal, firewood, and fodder, than in its native Israel (Kaplan, 1979). In Malawi, this species is already scorned by the rural public because it is thorny and difficult to work with. It is being tried for fencings (Nkaonja, 1980).

Ecology

Deemed the most promising of 56 Acacia species tried at Jodhpur, India. Probably ranging from Subtropical Desert to Dry through Tropical Desert Scrub to Very Dry Forest Life Zones, umbrella tree is reported to tolerate annual precipitation of 1 to 10 dm, estimated annual temperature of 18 to 28°C, and pH of 6.5 to 8.5. This species tolerates hot, arid climates with temperatures as high as 50°C subspecies raddiana grows where minimum temperatures are close to 0°C. It is best adapted to the lowlands. It thrives where rainfall is up to 1,000 mm. However, it is also extremely drought resistant and can survive in climates with less than 100 mm annual rainfall with long, erratic dry seasons. The tree favors alkaline soils. It grows fairly well in shallow soil, less than 0.25 m deep, though it develops long lateral roots that can become a nuisance in nearby fields, paths, and roadways. In shallow soil, the plants remain shrubby and must be widely spaced to allow for their lateral root growth.

Cultivation

For good seed germination, seeds should be treated with concentrated sulphuric acid for 30 minutes (Roy et al, 1973). Artificial regeneration aiming at large-scale nursery production requires full use of the germination capacity of the available seeds. This may be achieved by sulfuric acid pretreatment, which brings about the germination of all viable seeds. Treatment with boiling water is selective and mainly breaks the dormancy of bruchid-infested seeds, some of which are no longer able to germinate. Sowing of unripe seeds without pretreatment may be called for as an emergency measure in case of very severe infestation, to achieve at least partial success. Prior to storage, seeds should be fumigated to arrest progressing deterioration of seed viability by bruchids (Karschon, 1975). NAS (1980a) recommends dipping the seed in hot water to soak overnight. Seedlings require initial weeding to facilitate faster growth. Plantations can be spaced at 3 x 3 m.

Harvesting

Firewood harvested as needed, but 10-year rotations are suggested. In Jodhupr, flower initiation is ca May-June in 3-year old trees, fruits forming in July but ripening from November through February. Since the tree coppices well, there is no need to replant after every harvest.

Yields and Economics

Eleven-year old trees in deep sandy soils at Jodhpur averaged 6.4 m tall and 14 cm DBH. In shallow sandy loams over hardpan at Pali, India, 7-year old trees (98% survival) averaged 4.8 m tall, and 10 cm DBH. In sanddunes at Barmer, India, 5-year old trees averaged 3 m tall, 7 cm DBH. An average tree yields 6 kg pods of which 2.6 kg is clean seed. One tree is said to yield 14–18 kg pods and leaves per year in India (Muthana and Arora, 1980). Acacia tortilis has been reported to yield giraffe forage at 5 MT/ha/yr.

Energy

A 12-year-old plantation in India yielded 54 MT fuel , suggest, annual returns of 4.5 MT, not a bad return for the desert (NAS, 1980a). The heartwood has calorific value of 4,400 kcals/kg, making superior firewood and charcoal. It is one of the main firewood and charcoal sources in parts of Africa, e.g. around Khartoum. Nitrogen-fixing nodules are reported in South Africa and Zimbabwe.

Biotic Factors

Bruchids often damage or destroy the seeds, on the tree or after collecting. Herbivores, tame and wild alike, are liable to graze seedlings and innovations. Trees attacked by beetles, mimosoid blights, and caterpillars. The wood is susceptible to termites. In Tanzania, elephants which eat the bark are wiping out some park populations. In Israel, the native Acacias host several species (>40) of mostly monophagous insects, whereas on one exotic, Australian Acacia saligna, only a few polyphagous species occur (Halperin, 1980). Only Microcerotermes diversus and Kalotermes flavicollis, which feed on woody parts of both Acacias and Apate monachus (a beetle which tunnels the stems and branches, causing them to collapse in windblow), may seriously damage the tree. In nature, regeneration and spread of Acacias are probably limited by bruchids destroying much of the seed crop. Seedlings from natural regeneration may come from damaged seeds with a still intact embryo axis, since seedcoat dormancy is removed by the effect of exit holes permitting rapid water absorption and germination. Intact seeds with hard impermeable seedcoats may require a long time to germinate, and probably function as a reserve to ensure the survival of the species (Karschon, 1975).

References

  • Dalziel, J.M. 1937. The useful plants of west tropical Africa. The Whitefriars Press, Ltd., London and Tonbridge.
  • Gohl, B. 1981. Tropical feeds. Feed information summaries and nutritive values. FAO Animal Production and Health Series 12. FAO, Rome.
  • Halperin, J. 1980. Forest insects and protection in the arid zones of Israel. J. Israel For. Assoc. 30(3/4):68–72.
  • Kaplan, J. 1979. Some examples of successful use of Acacia for afforestation. J. Israel For. Assoc. 29(3/4):63–64.
  • Karschon, R. 1975. Seed germination of Acacia raddiana Savi and A. tortilis Rayne as related to infestation by bruchids. Ag. Res. Org. Leaflet 52. Bet Dagan.
  • Muthana, K.D. and Arora, G.D. 1980. Performance of Acacia tortilis (Forsk) under different habitats of the Indian arid zone. Ann. Arid Zone 19(1/2):110–118.
  • N.A.S. 1979. Tropical legumes: resources for the future. National Academy of Sciences, Washington, DC.
  • N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  • Nkaonja, R.S.W. 1980. Dryland afforestation problems in Malawi. J. Israel For. Assoc. 30(3/4):100–105.
  • Palmer, E. and Pitman, N. 1972. Trees of Southern Africa. 3 vols. A.A. Balkemia, Cape Town.
  • Roy, A.D., Kaul, R.N., and Gyanchand. 1973. Israeli babool a promising tree for arid and semiarid lands.

Acacia saligna (Labill.) H.Wendl

Uses

Orange wattle is an extremely rugged tree, adaptable to barren slopes, derelict land, and exceptionally arid conditions in Australia and North Africa. It grows rapidly and is used for reclaiming eroded hillsides and wastelands and for stabilizing drift sands as well as for fuel. This is one of the best woody species for binding moving sand. It is useful for windbreaks, amenity plantings, beautification projects, and roadside stabilization in semiarid regions. The leaves, or phyllodes, are palatable to livestock when fresh or dried into hay, especially used as supplementary feed for sheep and goats. Crushed seeds have been fed to sheep without ill effects. Regrowth of established bushes is so good that Acacia saligna can be completely grazed off without harming the plants. The damaged bark exudes copious amounts of a very acidic gum that seems to show promise for use in pickles and other acidic foodstuffs (NAS, 1980).

Folk Medicine

No data observed.

Chemistry

Natal-grown bark contains up to 30.3% tannin compared to 19.1–23.0 at the Cape. The plant has given negative test for HCN.

Description

Dense, bushy shrub, usually 2–5 m tall; may grow treelike to 8 m tall with a single main stem (diameter to 30 cm). In spring its usually drooping branches are clad in beautiful and abundant yellow flowers (NAS, 1980a).

Germplasm

Reported from the Australian Center of Diversity, orange wattle, or cvs thereof, is reported to tolerate alkalinity, drought, heavy soil, poor soil, salinity, salt spray, sand, shade, slope, waterlogging, and weeds. (2n = 26)

Distribution

Acacia saligna is native to the southwestern corner of western Australia. It was introduced to South Africa in the 1840s in an attempt to stabilize the shifting sand dunes. It has also been planted in Uruguay, Mexico Israel, Iran, Iraq, Jordan, Syria, Greece, Cyprus, and North African countries (NAS, 1980a).

Ecology

Acacia saligna can grow throughout the tropical and the warm temperate regions of the world (NAS, 1980a). In its native habitat, the summer temperature ranges from about 23°–36°C, winter temperatures from 4°–9°C. The plant does not withstand frost and grows best where the winter and summer means are between 13° and 30°C respectively. Grows from near sea level to about 300 m, with isolated occurrences at higher elevations. Particularly drought hardy, it grows where annual rainfall is as low as 250 mm, though it probably does better with 350–600 mm. It grows well where annual rainfall is as high as 1,000 mm. Grows mainly on sandy, coastal plains, but is found from swampy sites and riverbanks to small, rocky hills (often granitic) and coastal slopes. It occurs on poor acid or calcareous sands, under the most dry and adverse soil conditions, in moderately heavy clays and a range of podzols (NAS, 1980a).

Cultivation

Seeds germinate readily; young plants can often be found under mature trees in the hundreds. Seedlings are easily raised in a nursery and established in the field. This species develops root suckers and coppices freely. Seeds are normally treated with boiling water, but nicking the seed coat, soaking in sulfuric acid, and exposing the seeds to dry heat are also effective (NAS, 1980a).

Harvesting

In Mediterranean countries, the fuelwood from this species is harvested on a coppice rotation system of 5–10 years (NAS, 1980).

Yields and Economics

Acacia saligna grows quickly, often reaching up to 8 m tall with a spread as great as its height in just 4 or 5 years. In very dry situations, growth rate is slower. Annual yields vary from 1.5 to 10 m3 per ha, depending on site. Because of its hardiness and profuse reproductive abilities, Acacia saligna has become a serious menace in parts of South Africa by invading and displacing indigenous vegetation. It infests water courses (sometimes decreasing the water available for irrigation), and has proved difficult to eradicate (NAS, 1980a).

Energy

Plantations for fuel have been established in some Mediterranean countries. But, according to one report from South Africa, the wood is "sappy, light, and not a popular fuelwood." The plant can withstand some shade and can be grown as an understory beneath pines or eucalypts in energy plantations or village fuel and fodder areas (NAS, 1980a). The annual litterfall of four Acacia species naturalized in the South African Cape, comprising 60% foliage and 30% reproductive structures, averages 7 MT/ha, double the value expected in evergreen scrub communities in winter rainfall regions.

Biotic Factors

Acacia saligna supports a diverse and abundant range of herbivores that cause damage to the plant. Among pests cited are Icerya purchasi (Hemiptera) and Euproctis fasciata (Lepidoptera) (NAS, 1980a) and Meloidgogyne sp. (Nematoda)

References

  • N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.

Acacia senegal (L.) Willd.

Syn.: Acacia verek Guill. et Perr.
Mimosaceae
Gum Arabic, Senegal Gum, Sudan Gum Arabic, Kher, Kumta

Source: James A। Duke. 1983. Handbook of Energy Crops. unpublished.


Uses

Tree yields commercial gum arabic, used extensively in pharmaceutical preparations, inks, pottery pigments, water-colors, wax polishes, and liquid gum; for dressing fabrics, giving lustre to silk and crepe; for thickening colors and mordants in calico-printing; in confections and sweetmeats. Causing partial destruction of many alkaloids including atropine, hyoscyamine, scopolamine, homatropine, morphine, apomorphine, cocaine, and physostigmine, gum arabic might be viewed as a possible antidote. Pharmaceutically used mainly in the manufacture of emulsions and in making pills and troches (as an excipient); as demulcent for inflammations of the throat or stomach and as masking agent for acrid tasting substances such as capsicum; also as a film-forming agent in peel-off masks. Its major use is in foods, for example, as suspending or emulsifying agent, stabilizer, adhesive, flavor fixative, and to prevent crystallization of sugar, etc. Used in practically all categories of processed foods (candy, snack foods, alcoholic and nonalcoholic beverages, baked goods, frozen dairy desserts, gelatins, and puddings, imitation dairy products, breakfast cereals, and fats and oils). Use levels range from less than 0.004% (40 ppm) in soups and milk products, 0.7 to 2.9% in nonalcoholic beverages, imitation dairy, and snack foods, to as high as 45% in candy products (Leung, 1980). Strong rope made from bark fibers. White wood used for tool handles, black heartwood for weaver's shuttles. The long flexible strands of surface roots provide one of the strongest of local fibers, used for cordage, well-ropes, fishing nets, horsegirdles, footropes, etc. Seeds are dried and preserved for human consumption (NAS, 1980). Young foliage makes good forage. Plants useful for afforestation of arid tracts, soil reclamation, and windbreaks (Duke, 1981a). In modern pharmacy, it is commonly employed as a demulcent in preparations designed to treat diarrhea, dysentery, coughs, throat irritation, and fevers. It serves as an emulsifying agent and gives viscosity to powdered drug materials; is used as a binding agent in making pills and tablets and particularly cough drops and lozenges. Because of its enzyme, the gum is not suitable for use in products having readily oxidizable ingredients. For example, it reduces the vitamin A content of cod liver oil by 54% within three weeks. It is incompatible with aminopyrine, morphine, vanillin, phenol, thymol, a- and b-naphthol, guiacol, cresols, creosol, eugenol, apomorphine, eserine, epinephrine, isobarbaloin, gallic acid, and tannin; also with strongly alcoholic liquids, solutions of ferric chloride and lead subacetate and strong solutions of sodium borate. It was formerly given intravenously to counteract low blood pressure after hemorrhages and surgery and to treat edema associated with nephrosis, but such practices caused kidney and liver damage and allergic reactions and have been abandoned (Morton, 1977).

Folk Medicine

The demulcent, emollient gum is used internally in inflammation of intestinal mucosa, and externally to cover inflamed surfaces, as burns, sore nipples and nodular leprosy. Also said to be used for antitussive, astringent, catarrh, colds, coughs, diarrhea, dysentery, expectorant, gonorrhea, hemorrhage, sore throat, typhoid, urinary tract (Duke and Wain, 1981).

Chemistry

Gum acacia contains neutral sugars (rhamnose, arabinose, and galactose), acids (glucuronic acid and 4-methoxyglucuronic acid), calcium, magnesium, potassium, and sodium. Its complex structure is still not completely known. Its backbone chain consists of D-galactose units, and its side chains are composed of D-glucuronic acid units with l-rhamnose or l-arabinose as end units. The molecular weight has been reported to be between 200,000 to 300,000 and as high as 600,000 (Leung, 1980).

Toxicity

Ingested orally, acacia is nontoxic. However, some people are allergic to its dust and develop skin lesions and severe asthmatic attacks when in contact with it. Acacia can be digested by rats to an extent of 71%; guinea pigs and rabbits also seem to utilize it for energy, as does man to a certain extent. Gum arabic may actually elevate serum or tissue cholesterol levels in rats (Leung, 1980).

Description

Savanna shrub or tree, up to 20 m tall, over 1.3 m in girth, spiny; bark gray to brown or blackish, scaly, rough; young branchlets densely to sparsely pubescent, soon glabrescent, crown dense; stipules not spinescent; prickles just below the nodes, either in threes up to 7 mm long, with the middle one hooked downwards and the lateral ones curved upwards, or solitary with the laterals absent; leaves bioinnate, up to 2.5 cm long; leaf-axis finely downy with 2 glands; pinnae 6–20 pairs; leaflets small, 7–25 pairs, rigid, leathery, glabrous, linear to elliptic-oblong, ciliate on margins, pale glaucous-green, apex obtuse to subacute; flowers in spikes 5–10 cm long, not very dense, on peduncles 0.7–2 cm long, normally produced with the leaves; calyx bell-shaped, glabrous, deeply toothed; corolla white to yellowish, fragrant, sessile; pod straight or slightly curved, retrap-shaped, 7.5–18 cm long, 2.5 cm wide, thin, light brown or gray, papery or woody, firm, indehiscent, glabrous, 5–6-(-15) seeded; seeds greenish-brown. Fl. Jan.–Mar.; fr. Jan.–Apr., July, Aug. or Oct. (Duke, 1981a).

Germplasm

Tree with a single central stem and a dense flat-topped crown, bark without any papery peel, rough, gray or brown, with pubescent, rarely glabrous inflorescence, and pods variable in size, rounded to somewhat pointed but not rostrate or acuminate at apex. Variety rostrata Brenan is a shrub, branching at or close to base, or a small tree, with a single stem, 1–6 m tall, with dense flattened crown, bark normally with a flaking papery peel, creamy-yellow to yellow-green or gray-brown, inflorescence axis always pubescent and pods 2–3.5 times as long as wide, rostrate or acuminate at apex. Variety leiorhachis Brenan, is always a tree with central stem, and rounded or irregular with straggling branches; bark with conspicuous yellow papery peel, and inflorescence axis always glabrous. Variety pseudoglaucophylla occurs on fixed sand duned in Africa. Assigned to the African Center of Diversity, gum arabic is reported to exhibit tolerance to alkali, drought, fire, high pH, poor soil, sand, slope, and wind. (2n=26) (Duke, 1981a)

Distribution

Widespread in tropical Africa from Mozambique, Zambia to Somalia, Sudan, Ethiopia, Kenya, and Tanzania. Cultivated in India, Nigeria, and Pakistan.

Ecology

Thrives on dry rocky hills, in low-lying dry savannas, and areas where annual rainfall is 25–36 cm. This hardy species survives many adverse conditions, and seems to be favored by low rainfall and absence of frost. Ranging from Warm Temperate Thorn through Tropical Thorn to Tropical Dry Forest Life Zones, gum arabic is reported to tolerate annual precipitation of 3.8–22.8 dm (mean of 9 cases = 12.4 dm), annual mean temperature of 16.2–27.8°C (mean of 9 cases 23.8°C), and pH of 5.0–7.7 (mean of 7 cases = 6.4), but Cheema and Qadir (1973) report 7.4–8.2.

Cultivation

In Sudan, trees are cultivated over a very large area. Best propagated from seeds which are produced once every few years, grown in Sudan, in special "gum gardens." Elsewhere, it is collected from wild trees. In Pakistan, the best period for afforestation is the early monsoon season (Apr.–Jun.). Surface sowing is recommended in mildly alkaline sandy soils. Plants can also be reproduced by shoot cuttings. Trees coppice well (NAS, 1980).

Harvesting

Gum exudes froin cracks in bark of wild trees, mostly in the dry season, with little or none in the rainy season when flowers are out. In some areas, a long strip of bark is torn off and the gum allowed to exude. In Africa, it is regularly tapped from trees which are about 6 years old by making narrow transverse incisions in bark in February and March. In about a month, tears of gum form on surface and are gathered. Trees begin to bear between 4–18 years of age and are said to yield only when they are in unhealthy state due to poor soil, lack of moisture or damaged. Attempts to improve conditions tend to reduce yield. Gum from wild trees is variable and somewhat darker colored than that from cultivated plants. Collected gum is carefully freed of extraneous matter, sorted and sometimes ripened in sun before export. Gum arabic is oderless with a bland taste, yellowish and some tears are vermiform in shape. Ripened or bleached gum occurs in rounded or ovoid tears over 2.5 cm in diameter, and in broken fragments. Tears are nearly white or pale yellow and break readily with a glassy fracture. Gum is almost completely soluble in an equal volume of water and gives a translucent, viscous, slightly acid solution, but is insoluble in 90% alcohol. Kordofan (Sudan) Gum is yellow or pinkish, has fewer cracks and is more transparent (Duke, 1981a).

Yields and Economics

Annual yields from young trees may range from 188 to 2856 g (avg. 900 g), from older trees, 379 to 6754 g (avg. 2,000 g). Gum arabic is important export product for some areas in tropical Africa and Mauritania. From Africa some genuine gum is shipped to India then to Europe and America. Between 1940 and 1950, United States imports range from 3,179–8,989 MT (Duke, 1981a) Morton (1977) reports >11,000 MT more recently.

Energy

Considered the best firewood in Mauritius and Senegal, this is not a big yielder, annual running 0.5–5 m3/ha wood, with an energy value of ca 3,500 kcal/kg. A nitrogen,fixing species, it can be used to reestablish vegetation cover in degraded areas, as well as for sand-dune fixation and wind erosion control (NAS, 1980a).

Biotic Factors

Fungi reported on this crop are Cladosporium herbarum, Fusarum sp., Ravenelia acaciae-senegalae and R. acaciocola. Many insect visitors mimic the plant, the buffalo treehopper, Stictocephala bisonia, being a good example. Spiders (Cyclops sp.) may completely cover the young growing apex. Seedlings are often grazed by gazelles, goats, and pigs (Morton, 1977).

References

  • Cheema, M.S.Z.A. and Qadir, S.A. 1973. Autecology of Acacia senegal (L.) Willd. Vegetatio Vol. 27(1–3):131–162.
  • Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum Press. NewYork.
  • Duke, J.A. and Wain, K.K. 1981. Medicinal plants of the world. Computer index with more than 85,000 entries. 3 vols.
  • Leung, A.Y. 1980. Encyclopedia of common natural ingredients used in food, drugs, and cosmetics. John Wiley & Sons. New York.
  • Morton, J.F. 1977. Major medicinal plants. C.C. Thomas, Springfield, IL.
  • N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.

New Arid Land Ornamentals

Over the past decade, water conservation has become an increasingly important issue across the southwestern United States. This concern has led local horticulturists and landscape architects to explore the use of water-thrifty ornamentals from dry climates throughout the world. The Chihuahuan and Sonoran deserts in particular have yielded a vast array of successful landscape plants. Universities, growers, and plant enthusiasts have all participated in the collection, propagation, evaluation, and promotion of new plant introductions. A group of recent proven introductions, including trees, shrubs, ground covers, and perennials are included below with information on their origins, growth habits, cultural requirements, and potential uses in the landscape.

Acacia redolens Maslin, Desert CarpetTM

Acacia redolens Maslin, Desert Carpet

Native to inland areas of Western Australia, Acacia redolens Maslin has been used extensively in southern California and Arizona to cover large areas inexpensively. Seedlings of Acacia redolens vary widely in their growth habits, often reaching heights in excess of 1.8 m (6 feet). The Desert Carpet™ clone was selected from the first Phoenix freeway plantings for its prostrate growth habit, and was released by Mountain States Wholesale Nursery in 1984. Since that time, this groundcover has performed consistently on many projects, and years after installation has maintained a height of only 0.6 m (24 inches). One plant can spread to a width of 3.6 m (12 feet), although we have observed that the cutting-grown Desert Carpet™ plants are slower to establish and reach their mature size than seedlings. The slower growth rate and prostrate nature of this clone should reduce maintenance costs, since pruning is not necessary to control vertical growth. Instead of true leaves, Acacia redolens has thick, leathery, gray-green phyllodes. This plant blooms in the spring with small yellow flowers. Freeway acacia will tolerate low temperatures of –11.1° to –9.4°C (12°–15°F), alkaline and slightly saline soils, and does not seem to be choosy about soil types. In coastal areas it requires little or no supplemental irrigation, but does require regular irrigation in hot desert regions. Desert CarpetTM seems to be disease and pest free.


Baccharis hybrid 'Starn' (P.P.A.F.) ThompsonTM

Baccharis hybrid 'Starn' (P.P.A.F.) Thompson

When Dr. Tommy Thompson and Dr. Chi Won Lee of the University of Arizona released Baccharis hybrid 'Centennial', it filled a great void in our plant palette. Their research has been carried on, and now the improved Thompson™ clone is available. Since Baccharis 'Centennial' is a female plant, it has two undesirable characteristics. First, it produces pappus, or white "fluff," which litters the landscape and reduces the esthetic appearance of the plants for a short period of time. Also, since 'Centennial' is a female plant, it can be pollinated by nearby male Baccharis sarothroides Gray (Desert broom), and seedlings often result. This is why you sometimes see stands of 'Centennial' with taller Baccharis plants growing up through them. The ThompsonTM clone is a male plant, eliminating these two negative characteristics. Also, ThompsonTM was selected from the next generation after 'Centennial', and has 25% more Baccharis sarothroides for heat and disease resistance. The growth habits and uses of these two clones are essentially the same: both grow to about 0.9 m (3 feet) tall by 1.2–1.5 m (4-5) feet wide, are evergreen with bright green foliage and inconspicuous flowers, and provide a low-maintenance, long-lived alternative for difficult locations.


Cercidium species 'Desert Museum'

Cercidium species 'Desert Museum'

This hybrid palo verde is a three-way cross between Parkinsonia aculeata L., Cercidium microphyllum (Torr.) Rose & I.M. Johnst., and Cercidium floridum Benth. ex Gray, and seems to combine the best qualities of all three plants. 'Desert Museum' grows very rapidly to 6.1 m (20 feet) tall and wide in 3 to 5 years, after which it needs little or no irrigation. It is completely thornless, and produces very little litter, with few seed pods. It has a sturdy, upright growth habit which requires very little pruning or staking. It blooms over a long period of time, with the heaviest bloom from about mid-March to May 1. It also tends to bloom again in June and August. The yellow flowers are larger than any of its three "parents." It does not reseed like the messy Parkinsonia aculeata!


Chilopsis linearis (Cav.) Sweet, Lucretia HamiltonTM

Chilopsis linearis (Cav.) Sweet, Lucretia Hamilton

Desert willow trees occur along washes throughout the southwestern US and northern Mexico. This small deciduous tree has narrow, light green leaves that give it a weeping appearance. In the summer, the tree is covered with fragrant, trumpet-shaped flowers. In the wild, the flower colors range from white to purple, although a pale pink to lavender flower color is the most common. The Lucretia HamiltonTM clone was selected for its intense, deep pink to purple flower color, as well as its small stature. While many desert willow trees can grow to 7.6 m (25 feet) tall and wide, this clone seems to stay below 5.4–6.1 m (18-20 feet) tall and wide. After flowering, long narrow seed pods are produced. Plant Chilopsis linearis in full sun and well-drained soil, and in regions where temperatures do not drop below –17.8°C (0°F).


Chrysactinia mexicana Gray (Damianita)

Chrysactinia mexicana Gray (Damianita)

This small, compact shrub grows to 0.6 m (2 feet) tall and wide, and bears a very strong resemblance to turpentine bush, with needle-like green leaves and yellow daisy-like flowers. However, damianita blooms from March to September, while turpentine bush blooms from September to November. Combining the two plants would be a great way to prolong the color display! Damianita has wonderful-smelling foliage, and would be a great selection for sensory gardens. Damianita is a very tough, durable plant, tolerating extreme heat and cold, down to –17.8°C (0°F). Plant in full sun, and almost any soil. If this plant starts to look woody, prune it back severely in the early spring. Damianita ranges from New Mexico to west Texas and northeastern Mexico, at elevations of 609–2134 m (2000–7000 feet).


Dalea capitata Sierra GoldTM

Dalea capitata Sierra Gold

This well-behaved ground cover grows to about 20 cm (8 inches) tall by 0.9 m (3 feet) wide. Because of its compact size, Sierra GoldTM is a good selection for tight planting areas, such as small planters or medians. Its fine-textured, light green foliage has a fresh, lemony scent. Rabbits seem to avoid it! Yellow flowers carpet Sierra GoldTM in the spring and the fall. This plant is hardy to at least –15°C (5°F), but it will be deciduous at –3.9°C (25°F). The one drawback to this plant is that the whiteflies seem to like it, so some insecticide applications will be necessary in heavily infested areas around Phoenix. Plant in full sun for best results. No soil amendments should be necessary. In hot desert regions this plant requires some supplemental irrigation from spring to fall. Although most dales native to Arizona and Mexico tend to rot out if overwatered, we have observed this plant thriving right next to turfgrass, where it receives heavy irrigation. More testing is needed to determine if it will tolerate coastal areas, or regions with high rainfall.


Dasylirion longissimum

Dalea capitata Sierra Gold

This user-friendly accent plant is a great selection for high-traffic areas such as walkways and near entries. This grasslike plant does well in containers, and its symmetrical form provides a striking focal point. Its thin, stiff green leaves are completely unarmed, and have smooth edges. Eventually, its single trunk can grow to 1.8 m (6 feet), topped by a 1.5 m- (5-foot-) wide rounded head of leaves. The older, bottom leaves can be trimmed off to expose the trunk. Dasylirion longissimum is native to Mexico, and is hardy to about –8.3°C (17°F).


Euphorbia biglandulosa Desf. (Gopher Plant)

Euphorbia biglandulosa Desf. (Gopher Plant)

This evergreen perennial or subshrub has a very unusual form and appearance. Its arching stems angle out and up, and can reach a length of 0.6 m (2 feet). The plant grows to 0.9 m (3 feet) tall by 1.2 m (4 feet) across; with narrow, fleshy grey-green leaves. Broad clusters of chartreuse flowers occur at the tips of the arching stems, usually in the late winter and early spring. Flowers are followed by small brown seed pods that explode upon ripening. The stems usually die back after fruiting, leaving a small clump of grey-green foliage near the ground. Plant Euphorbia biglandulosa in full sun or light shade, in a well-draining soil. It is cold hardy to –15°C (5°F).


Hesperaloe parviflora (Torr.) J. Coult., 'Yellow' (Yellow yucca)

Hesperaloe parviflora (Torr.) J. Coult., 'Yellow' (Yellow yucca)

A clumping perennial with long, gray-green leaves, Hesperaloe parviflora grows slowly to form a grasslike clump 1.0–1.2 m (3–4 feet) tall and wide. From spring through fall, it produces 1.5 m- (5-foot-) tall flower spikes. Red-flowering plants have been a staple in southwestern landscapes for many years. This is simply a yellow-flowering selection. Use this tough accent plant in full sun. Since it also tolerates reflected heat, yellow yucca is a reliable plant to use along sidewalks, in parking lots, etc. Tolerant of temperature extremes, yellow yucca is cold-hardy to at least –17.8°C (0°F). Once established, it requires little or no irrigation. All in all, yellow yucca is one of the toughest and most maintenance-free plants.


Hymenoxys acaulis (Pursh) K. Parker (Angelita Daisy)

Hymenoxys acaulis (Pursh) K. Parker (Angelita Daisy)

This perennial is native to the southwestern US, where it occurs most often at elevations from 1219–2134 m (4000–7000 feet), on dry rocky slopes and mesas. Angelita daisy bears a strong resemblance to Baileya multiradiata Harv. & A. Gray ex Torr. (desert marigold). However, the foliage is green rather than gray, and the flower is a deeper gold color. Forming rounded clumps to fifteen inches tall and wide, Hymenoxys acaulis is a wonderful plant to use as a border in front of larger shrubs. I f water is available, it will naturalize in the landscape. In Phoenix, this plant blooms all year, with especially heavy bloom in the spring and fall months. This prolonged bloom period results in many dried flower stalks, which can make the plants look scruffy. We recommend cutting off the old flower spikes occasionally to rejuvenate the plant and initiate new flower production. Angelita daisy seems to prefer well-drained soils and full sun. It is very cold hardy, heat tolerant, and drought tolerant.


Leucophyllum candidum I.M. Johnst. Thunder CloudTM

Leucophyllum candidum I.M. Johnst. Thunder Cloud

As with all of the other Leucophyllum species, this clone blooms when the humidity is high. The silver, pubescent foliage is a perfect foil for the masses of indigo flowers that appear in the summer and fall months. Thunder CloudTM was selected and trademarked by Benny Simpson of Texas A&M University. His clone is highly valued because of its small, dense growth habit. Unlike most of the larger Leucophyllum species, Thunder CloudTM remains reliably small, to three feet tall and wide. This plant is cold hardy to at least –12.2°C (10°F). Plant all of the Leucophyllum species in full sun and well-drained soil. Avoid overwatering.


Leucophyllum langmaniae Rio BravoTM

Leucophyllum langmaniae Rio Bravo

Trademarked by Mountain States Nursery, this clone has a nice, compact growth habit very similar to L. frutescens 'Compacta'. Rio BravoTM has become very popular because of its bright green foliage and rounded, dense form. It has lavender flowers and will eventually grow to 1.5 m (5 feet) tall and wide. Like the L. candidum species, it requires well-drained soils and full sun. It is hardy to –12.2°C (10°F).


Muhlenbergia capillaris (Lam.) Trin. Regal MistTM

Muhlenbergia capillaris (Lam.) Trin. Regal Mist

We feel that this ornamental grass shows great promise for many different regions of the country. Native to humid southeastern Texas, this grass has adapted extremely well to the hot, dry conditions of deserts in Arizona and Nevada. In fact, it has performed incredibly well in Las Vegas, which is cursed with poor soils, high winds, high summer temperatures, and cold winters. Regal MistTM is also happy in heavy soils, with ample irrigation. In short, it has worked everywhere it has been tried, so far! It is hardy to at least –17.8°C (0°F). Regal MistTM has narrow, dark green, glossy leaves. It grows quickly to form a rounded clump to 0.9 m (3 feet) tall and wide. The flower spikes on this grass have attracted a lot of attention... they form misty masses of pink to purple flowers in October and November. We recommend cutting this plant back in early spring to cut off the dead flower spikes and any dormant foliage.


Penstemon species

Penstemon species

There are so many wonderful Penstemon species to try in the garden, that is difficult to select just a few. Most of the penstemons are perennials with a basal rosette of foliage, which send up spikes of tubular flowers in the spring and early summer. They add incredible color to the landscape, and attract hummingbirds as well! Penstemons come in a wide range of colors, including blue, purple, pink, and red. After they finish blooming, allow the flower spikes to dry on the plant. Then cut off the spikes and sprinkle the seed in the garden to increase next year's mass of color. There are two new species to try: Penstemon triflorus Heller, which has short, 46 cm (18 inch) spikes of dark pink-purple flowers which occur along the stem in clusters of three; and Penstemon clevelandii Gray, native to southern and Baja California, with spikes of clear, bright pink flowers to 0.6–0.8 m (2–2.5 feet) tall.