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Lost Crops of Africa: Fruits, Volume III
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Lost Crops of Africa: Fruits, Volume III 7 MARULA Not for nothing is marula (Sclerocarya birrea) dubbed “food of kings.”1 In the giant triangle from Cape Verde in the west to the Horn of Africa in the east and to the Cape of Good Hope in the south, its prized fruits and macadamia-like seeds are in demand. Many Africans consider a gift of marula nuts a sign of signal friendship. In some societies, the tree ranks as a major food supplier, its economic and social importance being such that they are said to have a “marula culture.”2 Marulas are plum-sized stone fruits with a thick yellow peel and translucent white flesh. Many are eaten fresh but most are processed into things such as beverages, jams, and jellies. Although the succulent pulp has its own flavor, writers searching for a frame of reference have variously described it as being like litchi, apple, guava, or pineapple. Regardless of taste, the juice is nutritionally important, containing as much as four times the vitamin C of orange juice. The kernels inside the stone that is found at the center of the fruit are also eaten. They too have high nutritive value, not to mention a delicate taste and such exceptional oil content that they burn like a bright candle. These nuts provide tasty sustenance for both human and beast. Given these products, marula is at once a fruit tree and nut tree—a sort of tuck shop on a trunk. It is also a good food-security resource. Especially significant in this latter regard is the fact that it provides food during the season when grain stocks are low and other crops have yet to reach harvestable form. It is also significant that the nuts store so well they provided nutritious food long after all else is gone. The living tree is remarkable in its own right. When fully grown it is large and shady. People genuinely like having it around for its shade and beauty as well as for its fruits. When farmers clear the land, these trees are often all they leave standing. Marula has long been also planted deliberately. 1 This is a common Bantu description of marula. It is, for instance, the name given it by the Tonga, who live in Mozambique as well as in the neighboring parts of South Africa and Zimbabwe. 2 This has been said of the Phalaborwa, for example. Krige, E.J. 1937. Note on the Phalaborwa and their marula complex. Bantu Studies 11:357-366.
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Lost Crops of Africa: Fruits, Volume III Oshakati, Namibia. Throughout much of Africa marula fruits and seeds are in high demand. In some regions, the tree ranks as a major food supplier. The large and spreading tree is treasured for its shade and beauty, not to mention its foodstuffs. This is an exceptionally drought resistant species, and its resistance to heat, harsh sunlight, and difficult conditions is legendary (Klaus Fleissner) It grows with great vigor. It thrives under exceptional heat. And it tolerates some of the most inhospitable terrain known to horticulture. Marula fruits are not picked: they harvest themselves by conveniently falling off while still green and hard. They hit the ground without bruising, and subsequently ripen within about five days. It is common for farmers to build elaborate fences or to pile thorny branches around their trees to keep animals from reaching the fruits first. Although when fully ripe the pulp turns pleasantly sweet-and-sour— something like an orange—most of the fruits tend to be tart. Some marulas come with a slight turpentine aftertaste, a feature not universally admired. The scent is applelike and rather pleasant, but can become overpowering where there are large quantities of over-ripe fruits. But few of these fruits are eaten raw. Most end up in various kinds of drinks. Adding the juice to water, for instance, produces a refreshing squash. If set aside for a few days this liquid ferments into a hard cider. Although both tasty and nutritious, the result can be also highly intoxicating. Marula-juice beverages—both soft and hard—have been commercialized in South Africa. The amounts produced are surprising (at least considering that this is a “lost” crop and as-yet is little grown in organized production). In a recent year, for instance, about 500 tons of marulas were commercially processed for juice and 2,000 tons for liqueur just in South Africa. Beyond drinks, the
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Lost Crops of Africa: Fruits, Volume III fruit is popular for amber-colored jellies. These are so treasured that purveyors charge gourmet prices and peddle them to upscale food fanciers. Marula is in the same botanical family as cashew and pistachio (not to mention mango) and, like those famous relatives, could become a widely grown nut tree. Indeed, the kernels inside the seed are often more sought-after than the flesh around them. In flavor, they resemble macadamia, and are considered a treat special enough for serving revered guests. Furthermore, marula nut is nutritious enough to outscore even southern Africa’s acclaimed mongongo nut.3 An important feature is that marula seeds keep for months without deteriorating (at least if clean and completely ripe). Throughout the plant’s range, and especially where cereal crops grow unreliably, piles of them can be seen in the villages as emergency food caches. As long as the seeds remain dry, they stay wholesome: neither fungi nor insect are capable of penetrating the rock-hard shell. As earlier noted, the kernels are rich in oil, averaging about 55 to 60 percent. The oil itself is high in unsaturated fatty acids, typically containing 70 percent oleic acid and 8 percent linoleic acid—excellent numbers indicating an elite vegetable oil. Beyond good lipids, the kernel contains considerable amounts of protein (23-31 percent). The nut also provides minerals such as calcium, magnesium, phosphorus, and (to a lesser extent) potassium and sodium.4 Given all these nutritional components, marula nuts could be a big-time commercial resource—perhaps even globally enjoyed like cashews. However, breaking them out of the shell is a major problem. The seed’s woody outer coating is both thick and hard, making the nuts difficult to extract intact. Although the plant yielding this wealth of foodstuffs occurs over a range of southern and tropical African habitats, it is concentrated mainly in patches of hot, dry, open woodlands. It comes in two distinct types: one indigenous to the southern region is botanically known as subspecies caffra and the other, native further north, is subspecies birrea.5 The southern type constitutes the main subject of this chapter. More limited in location, it is nonetheless more developed as a crop. Although not domesticated in the standard sense, marula is indeed cultivated. For hundreds of years, Africans have planted it, and in places its distribution overlaps almost perfectly with human migration patterns. In 3 Marula nuts can produce up to 750 calories per 100 gm, compared with about 640 for mongongo nuts. They also have higher protein and fat contents. Compared to mongongo nuts, of course, marula nuts are less abundant, harder to extract, and much smaller in size. 4 Wehmeyer, A.S. 1966. The nutrient composition of some edible wild fruits found in the Transvaal. South African Medical Journal 40:1102-1104. 5 There is also a subspecies multifoliata, which is intermediate between the two. It is found in Tanzania and probably Kenya.
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Lost Crops of Africa: Fruits, Volume III Marula soaks in the unrelenting sun of arid climes, where it grows with great vigor. It thrives under exceptional heat and tolerates some of the most inhospitable terrain known to horticulture. Marula fruit can be eaten fresh but most is made into beverages, jams, and jellies. The flavor is described as being tart, sweet, and refreshing, with a similarity to apple or pineapple. The kernels inside the seeds are often compared with macadamia nut. (Elaine Solowey) other words, people liked it so much they carried seeds with them and planted it along the wayside as they went. Moreover, in countries such as Namibia, the majority of trees that appear to be scattered around in the wild are actually owned by particular families. And the fact that the trees are mostly females indicates a human influence, because only females bear fruits. The practice of growing elite genotypes from cuttings is part of traditional knowledge as well.6 Given such features it can be said that marula (i.e., the southern type) is at least on the first rung of the ladder to domestication. Moreover, horticulturists in South Africa have selected and cloned superior types over the past 25 years. Indeed, some of those clones are entering intensive cultivation in both South Africa and Botswana. This crop is also undergoing trials and horticultural development at introduction orchards established at four locations in Israel’s Negev Desert. There are good reasons for thinking marula worthy of further development. For one thing, the species can be extremely productive. In South Africa, as many as 91,000 fruits have been counted on a single tree in a good year.7 In Namibia 4.5 tons of fruit have been measured in single season on a single large tree.8 6 Information from Pierre du Plessis. 7 This figure is in Quin, P.I. 1959. Foods and Feeding Habits of the Pedi. Witwatersrand University Press, Johannesburg. This is by no means an average yield, however. 8 Information from F.W. Taylor and N. Baker.
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Lost Crops of Africa: Fruits, Volume III For another, shelling the nuts provide work for thousands of rural women with hardly any other source of income. And for a third, there exists considerable commercial demand for both fruits and nuts. In Namibia, Botswana, Zimbabwe, and South Africa, many fruit are collected and sold by villagers to the rising number of facilities that have been established to process marula, with some handling over 1,000 tons of fruit a season. Pulp is already appearing in mainstream commerce in the form of juices, jams, jellies, puree, and liqueur. Oils are also extracted from the nuts and put into pricey skin products, a process pioneered in Namibia, which even exports marula oil for this purpose. PROSPECTS Presently marula is considered a subtropical crop of limited adaptation but considerable promise. Both its adaptation and commercial possibilities may soon be much clearer because the rising popularity of a fruit-juice drink and a liqueur has stimulated horticultural interest all across southern Africa. Although the fruit’s clingstone quality means that it is best for processing into such things as juice, jelly, and beverages, its pleasant apple-like odor and litchi-pineapple-guava flavor, not forgetting its nutrient content, would seem to justify confidence in its prospects for much wider use. Within Africa How well the southern marula will do in the other parts of Africa is presently unknown. Possibly it will perform in stellar fashion. Here are likely scenarios. Humid Areas Uncertain prospects. The southern subspecies appears ill-adapted to high humidity. The northern counterpart, however, is a possible new resource for hot and hard conditions. Already, it is being planted quite extensively in Zambia. Dry Areas Excellent prospects. Marula tolerates saline water and grows with vigor in desert heat. The trees continue bearing even during droughts, although dryness makes the fruits somewhat smaller. Once established, however, the trees are almost never killed by desiccation. Upland Areas Uncertain prospects. The plant is somewhat frost-tender, but there may be locations where it safely fits the climate. Beyond Africa How well this plant will perform and how well its fruit and nut will be accepted in lands beyond Africa is unknown and uncertain. Nonetheless, small-scale trial plantings are warranted in locales to which it is suited.
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Lost Crops of Africa: Fruits, Volume III Marula fruit pulp serves as a flavorful natural base for fruit soft drinks, nectars, and teas; alcoholic beverages such as brandies, liqueurs, beer, wines and punches. Marula is already also appearing in commerce in the form of juices, jams, jellies, puree, and liqueur. (Cori Ham) USES Marula primarily provides fruits and nuts, but those are really just a start. Consider the following. Fresh Fruits The fruits are eaten fresh in many parts of subtropical southern Africa. They are sometimes cooked. The juice not only makes an agreeable drink; it is often boiled down into thick black syrup, used mainly for sweetening sorghum gruel. The flesh can also be dried and stored for later use, when it is typically added to cereal porridge. Processed Foods Drinks made from marula are everywhere popular. Many places boast of their local marula beer.9 In southeastern Zimbabwe, for example, it is called “mukundi” and it is much liked. In Swaziland, a very potent marula drink is so popular it drastically affects the local 9 The fruits ferment so fast there is a common belief they intoxicate wildlife. However, this is now thought possibly untrue or even a ploy to entice tourists. See, for example, de Klerk, W.A. and T.G. Watson. 1974. Baboons and marulas. Custos 3(9):33-37.
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Lost Crops of Africa: Fruits, Volume III breweries’ beer sales during the fruiting season. In Namibia there is an official marula wine season during which no one is allowed to carry traditional weapons and crimes are punished with double the usual punishment. A distillate for the more sophisticated palate has been developed in South Africa. An “Amarula Cream” liqueur is now available not only in local markets but in international trade. Nuts Marula nuts are used to flavor dishes of meat, greens, and porridge as well as being pounded into flour and pressed into cakes. The kernels can also be used like walnut or pecan in baking. They are especially used to provide protein and dietary energy during the “hungry season”—the time before the staples can be harvested. Vegetable Oil The oil extracted from the kernel has a fatty acid profile similar to olive oil. It is not only high in monounsaturation, but is relatively low in tocopherol and thus has exceptional stability. On the basis of its chemical makeup, marula oil is well suited for use in frying, cosmetics,10 or coatings on foods such as dried fruit.11 Presently, it is too expensive to succeed as common cooking oil, but might find a niche market as a specialty salad oil. It may also find greater use in cosmetics; it is “non-drying” and reportedly seems to have properties that combat the aging of skin. Because of its reputed antibacterial action marula oil is used to treat wounds and burns. It is also used as a preservative for biltong (dried meat). Forage Stock farmers love having marula trees dotting their property. This big, leafy tree provides great shade and its fruit, leaves, and bark make excellent fodder, especially welcome during times of drought. For wildlife, the marula is also important, constituting a living, renewable pantry for hordes of herbivores and omnivores—from elephant, rhinoceros, giraffe, and kudu to warthog and hedgehog. Baboons are particularly fond of picking up the ripe fruit scattered under the trees. Flowers Flowers produce nectar in quantity, making the tree an important resource for beekeepers. The honey is light-colored with excellent flavor. Wood The wood hardens as it seasons, eventually becoming durable and strong. Although dirty white, with red and brown streaks, it turns a pretty pink when polished. Carvers make it into drums, stamp-blocks, troughs, spoons, stools, bowls, and more. Because it is easy to work and does not splinter, it was once popular for toilet seats—so popular in South Africa that the tree almost became a threatened species. 10 Information from Cyril Lombard, CRIAA SA-DC, Namibia. 11 Burger, A.E.C., J.B.M. de Villiers, and L.M. du Plessis. 1987. Composition of the kernel oil and protein of the marula seed. South African Journal of Science 83:733-735.
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Lost Crops of Africa: Fruits, Volume III Other Marula root brews have renown as antimalarial tonics. In some villages, parts of the tree are apparently employed against lice. NUTRITION Although marula fruit pulp is an important source of micronutrients, vitamin C is what makes it nutritionally interesting. The flesh commonly contains 180 mg vitamin C per 100 g, but the concentrations can go even higher. In this regard, the marula outshines orange, grapefruit, and lemon. At 2 mg per ml of juice (about the amount of juice found in one fruit), it is an especially important source of this essential nutrient. Carbohydrate levels of between 7 and 16 percent have been recorded in the fruit pulp.12 The carbohydrate consists mainly of sucrose, with smaller quantities of glucose and fructose. The acidity is due mainly to vitamin C (ascorbic acid) and citric acid.13 Nutritionally speaking, marula has something oranges lack—a good-tasting nut. Rich in food energy, the kernel normally contains around 700 calories per 100 g and surpasses the nutritive content of globally famous nuts such as almonds, chestnuts, and hazelnuts. Because of their fine taste, marula nuts are described as a delicacy. Their fat, protein and mineral contents make them a useful dietary supplement during winter or droughts. They are exceptionally nutritious, with 28-31 percent protein, 56-61 percent oil, 2.02 percent citric acid, malic acid, and sugar, phosphorus, magnesium, copper, zinc, and B vitamins (thiamine and nicotinic acid). Protein levels of 54-70 percent have been reported for defatted nutmeat.14 HORTICULTURE Seeds mature (inside the fruits) in late summer, and, after a few months of dormancy, are easily germinated if subjected to heat (around 30°C) and moisture. Vegetative propagation is in its infancy, but Israeli horticulturists have found that propagation via root cuttings is very easy.15 Such techniques can be used to clone elite specimens as well as to avoid the long juvenile periods that growers of seedlings must suffer. The plant can also be propagated by 12 Jaenicke, H and M.K. Thiong’o. 2000. Preliminary nutritional analysis of marula (Sclerocarya birrea) fruits from two Kenyan provenances. Acta Horticulturae 531:245-249. 13 Weinert, A.G.I., P.J. van Wyk, and C.L. Holtzhausen. 1990. Marula. Pp. 88-115 in Nagy, S., P. Shaw, and W.F. Wardowski, eds., Fruits of Tropical and Subtropical Origin. Florida Science Source, Lake Alfred, Florida. 14 Burger et al., 1987, op. cit. 15 Information from A. Nerd.
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Lost Crops of Africa: Fruits, Volume III jabbing sections of large branches into the ground during the wet season. These so-called truncheons are usually about 2 m long and 10 cm in diameter, and are planted 60 cm deep. If cut at the time of bud swelling they strike readily, putting out abundant roots with speed and vigor. Grafting branch wood from one plant onto seedling rootstocks of another (using terminal grafts) is reportedly very successful. The operation is made just as new spring growth is beginning. Such grafts, covered with sealant, have resulted in almost complete success (98 percent with one cultivar). Marula trees in general have few pests or diseases. Indeed, they are thought to be infused with insecticidal ingredients. However, a pesky fruitfly invades the ripe fruits, which are also attacked by the caterpillars of at least two moth species. HARVESTING AND HANDLING By and large, the fruits are easy to handle because they are firm when they fall from the tree. At that point the skin is tough enough not only to resist bruising from the fall but to give the fruit a good shelf life. Observations in Israel indicate that although different trees drop their fruits at different times, each drops 80 percent of its fruits within two weeks. Yields can be outstanding. As much as a ton of juice has been obtained from the fruits from a single tree. The juice can be separated by standard techniques, such as the rack-and-cloth press method. Using modern technology, the South Africa’s National Food Research Institute has developed a process for making marula juice on a large scale. Not unexpectedly, storage temperatures affect the way the fruits ripen. In tests, fruits kept at 12°C and at 20°C developed a yellow color and were suitable for juicing. Those stored at the higher temperature were the ripest. They had a deeper yellow color, a higher juice content, and lower acidity. Fruits kept at 4°C remained green and firm for 14 days, and seemed undamaged, but after five days at room temperature (20°C) they developed brown spots and an off-flavor.16 The nuts, on the other hand, are difficult to handle. Shelling the peach-stone-like seeds and extracting the kernels inside is almost an art. Some experienced locals use thorns for the task; others employ special metal, wooden, or bone “teaspoons” or extractors (often even suspended from a necklace in marula season) after they have opened the seeds—either by bashing them between two stones, or by chopping off one end against an axe. They become quite deft at winkling the kernels out; boiling or lightly roasting the seeds makes the whole process easier. Boiling causes the cap sealing the embryo chamber to expand so it can be more easily removed, while roasting makes the stone so brittle that striking it makes the caps jump out to expose the kernels inside. 16 Information from A. Nerd.
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Lost Crops of Africa: Fruits, Volume III LIMITATIONS Marula fruits and seedlings are favorites of many animals; all plantings therefore need careful protection. In southern Africa, elephants are among the principal seed-dispersing agents. Elephants also sometimes debark trees, which nonetheless heal themselves well. Giraffe and antelope (notably kudu, and nyala) also browse both leaves and fruits. Goats are such a serious threat to young trees that no self-sown seedlings are found anywhere near villages. Although most people consider the fruits delicious, some are disappointed that there is not more pulp and less juice. This could be corrected through selection, but supreme juiciness is also a virtue. Clearly, it depends on what one wants, likes, or expects. A more serious limitation is that fact that the flesh adheres firmly to the stone. As in mangos or the peaches of earlier times, soft fibrous strands attach the pulp to the stone. The size of the stone is another flaw; it is quite large for the overall volume of the fruit. In addition, the thick skin detracts at least a little from the volume of pulp. Given that most marulas are currently planted from seeds, there is a long delay between planting and production. This is a major limitation to new plantings, which is avoided with clones. The ripe fruits can have a strong smell, which one either likes or dislikes. In over-ripe specimens, fermentation can make it worse. Although the nuts have exciting promise, a major problem is their relatively low productivity. The kernels are small compared with the size of the woody shell around them. As a result, stones weighing 1 ton yield only 40 kg oil and 40 kg edible protein. NEXT STEPS This species seems a great resource for alleviating poverty and diversifying rural livelihoods. It has a recognized commercial value and it keeps people and animals alive by providing vital nutrients during times of famine. However, although it is not quite a “lost” crop, there are still many uncertainties about its products and vast unknowns about its performance. This opens different research opportunities, not all of them requiring professional researchers. The following highlights areas of need. Commercial Development For this much-beloved plant, achieving greater production lies less with science than entrepreneurship, motivation, and investment. The horticultural side is relatively straightforward; processing is in need of some work but it is also basically in hand. However, the market remains underdeveloped and still needs lots of development. Marula need not be grown only in orchards or for strictly commercial ends. Indeed, it represents a major income opportunity for rural communities throughout Africa, and development work should focus on systems that will
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Lost Crops of Africa: Fruits, Volume III Although oils are extracted from marula nuts and put into pricey skin potions around the world, currently marula’s juicy pulp yields the most commercially successful product–a cream liqueur. Whole fruit is collected from the veld by local villagers, providing them seasonal income. Next, skin and stone are separated from the flesh, which is then carefully fermented like grapes. The resulting marula wine, mixed with fruit solids, is distilled in copper pot-stills and matured in small oak casks for about two years, capturing the unique flavors of marula in concentrated form. The final step is blending the liqueur with fresh cream. The result is a smooth, stable, luscious cream liqueur marketed in about 150 countries. ( Distell Group Limited) facilitate community-level production. Nonetheless, bigger commercial markets will provide income opportunities for rural producers lacking the space or capital to plant thousands of trees for commerce. And beyond that, marula can contribute to rural development on many levels, not to mention nutrition and food security for people lacking the money to buy food. Fodder This is one of the most ancient of all fodder trees and yet the leaves’ feed value is all but unknown. Needed now are standard nutrient analyses. These are often an excellent way to get a crop developed. Practical
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Lost Crops of Africa: Fruits, Volume III developments are likely to follow spontaneously, as farmers with livestock are exceptionally motivated to follow up on promising forages because for them no feed means no livelihood. Selection As far as commercial progress is concerned, this is the most powerful area for research endeavors. Further selection of outstanding wild trees for production of fresh fruit, processed fruit products, and nut is needed. A larger fruit having a smaller stone and perhaps a thinner skin would obviously be more desirable for most purposes. Also, selections with improved precocity and higher yield would be most welcome. Vegetative Propagation Cloning, including truncheons, is key to making this crop work. For one thing, it improves fruit quality and dramatically reduces the delay between planting and first harvest. The techniques seem to be on hand already. For instance, hardy but inferior fruited trees can be used as rootstocks for selected scions of superior plants. Needed now is engagement by the nursery trade and amateur horticulturists so that top selections become widely available to backyard and orchard-level growers. Control of Pests While this plant is not normally pest ridden, reliable methods for combating marula fruit fly (Ceratitis cosyra, also a mango pest) would strengthen its future. Food Technology Many food technologies remain to be applied to marula. A key one is the processing of the nuts. Practical methods for extracting the kernels need to be developed. They need not involve a high-tech decorticator. A cheap and simple—but still relatively labor-intensive technology suitable for rural homesteads—would be ideal. Rural women could then decorticate their own seeds in their own time. Genetic Development There seems to be much genetic variation in the species, and this is a good time to establish gene banks wherein differences between promising specimens can over time be observed and exploited. It is difficult to prefigure a crop’s future direction, but four possible directions have been especially suggested for developing marula by combing through the existing germplasm and selecting types whose fruits are:17 Large (over 80 grams) with good taste and thick pulp (for use as fresh fruit and for making fruit leather and marmalade). Very juicy (for things such as nectar, syrup and fruit drinks). Rich in sugar (for production of alcoholic drinks). Large-seeded (for oil production) 17 These suggestions are primarily from one of our contributors, Elaine Solowey
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Lost Crops of Africa: Fruits, Volume III In addition to the selection and propagation of superior individuals, it is valuable to alter the sex ratios in the stands, from the usual male predominance to roughly one male to five females. Reforestation Marula is excellent for revegetation purposes. For instance, in Israel marula is becoming widely planted. For years the Jewish National Fund’s reforestation department has distributed saplings for land reclamation, roadside groves, and windbreaks. Nowadays, this small African tree is to be seen binding up scars of deforestation and desertification in many locations.18 This particular use is poorly appreciated within Africa, where it deserves immediate inclusion in trials and reforestation programs. Physiology In these early stages of the plant’s commercialization, no one knows the outer limits of the marula’s adaptability to climate and soil. Tests are warranted throughout much of the African continent. The key finding has less to do with the plant’s survival than with its commercial viability. Phenology Marula could become a great agroforestry species. Rural Africans love the tree and millions would plant more of it on their farms. Needed, though, is a better understanding of the timing of leafing, blossoming, fruit drop, and other seasonal features at various likely locations. The tree’s compatibility with neighboring crop plants also needs general assessment. It is especially important to find male plants that provide pollen at the very time that superior female plants are in blossom. Subspecies performance Botanists have divided this species into subspecies based on observations of visual differences. Now is the time to better understand the true genetic differences and performance requirements of each. Out of this likely will come many surprising and intriguing facts that could greatly enhance marula’s use in the hotter, drier, more northern African regions. Perhaps, too, hybrids between subspecies caffra and subspecies birrea are possible, bringing great benefits to both. 18 Information from Elaine Solowey.
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Lost Crops of Africa: Fruits, Volume III SPECIES INFORMATION Botanical Name Sclerocarya birrea (A. Rich.) Hochst. especially S. birrea subsp. caffra (Sond.) Kokwaro19 Family Anacardiaceae, the Mango Family. Synonyms Sclerocarya caffra Sond.; Poupartia birrea (A. Rich.) Aubrev.; Spondias birrea A. Rich. Common Names Afrikaans: maroela, olifantsappel Arabic: homeid Bantu: mupfura Botswna: morul Burkina: noabega (Moré) English: marula or elephant plum, morula, cider tree French: prunier Mali: kountan, kountango (Bambara); bi (Dog.) Malawi: mefula Mozambique: mudângwa (center), canhu (south) Niger: eedi, diné, dinégna (Sonrai) Senegal: bire (Wolof), beur, biét (Ouol.); aritj (Sér.) Setswana: morula Shona: mutsome, mupfure Swaziland: buganu (name for both tree and the drink made from fruit) Zambia: musebe, muongo, msewe Zimbabwe: mganu (Matabeleland), managahn, bufuna, musomo Zulu: unganu (which means friend) Namibia: Omuongo (Oshiwambo) Description This handsome, shapely, deciduous tree is often but not always single-stemmed and sometimes reaches 20 m in height. The mature tree’s bark is distinctive—rough and mottled in appearance because it peels off in disc-shaped flakes. The compound leaves are aggregated at the end of short branches and blunt twigs. They are pale green on the lower surface and shiny dark green on the upper one. The species is dioecious, meaning there are separate male and female trees. However, cases of self-fertile hermaphrodite trees producing some 19 Sclerocarya birrea subsp. caffra occurs naturally in Southern Africa; subsp multifoliolata in central Tanzania; subsp. birrea in West Africa and into Tanzania.
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Lost Crops of Africa: Fruits, Volume III fruit have been reported. The female flowers are located at the end of short twigs. One to three flowers occur in a cluster. The smooth, ovoid fruit sometimes reaches 5 cm in diameter, but is most often about half that size. On average, they weigh 30 g but selected trees yield fruits weighing up to 100 g. As they ripen the leathery green skin turns pale yellow and develops inconspicuous minute rough spots (lenticels). The flesh is white and juicy. The flesh covers a large attached stone, which is usually two-chambered, each chamber containing a seed. The root system is well developed and the roots are succulent. They store quantities of water and starch, lending tolerance to drought and hard times. Distribution Species Sclerocarya birrea has a wide distribution in Africa—from Senegal in the west to Sudan and Ethiopia in the north and to the Swaziland and coastal Natal in the south. However, the particular subspecies (caffra) that has attracted the most horticultural attention is native only to the southern part of this range, mainly Botswana, Mozambique, Namibia, South Africa, Swaziland, and Zimbabwe. Horticultural Varieties A number of improved clones producing large fruits weighing up to 100 g and with a variety of skin colors are known in South Africa and neighboring nations. Environmental Requirements This is an exceptionally drought tolerant species, and its resistance to heat, harsh sunlight, and difficult conditions is legendary. Rainfall Generally speaking, marula is found in arid to semiarid areas with a (mostly summer) rainfall, varying from 250 to some 1,000 mm. In South Africa, the plant is said to be best suited to the 250 to 800 mm rainfall zone. In Botswana, it is found naturally within the 400-650 mm rainfall range. In Namibia, 250-350mm per annum is the norm. The roots store water and the rainfall of the previous season is possibly more important to the harvest than is that of the current fruiting season. Altitude Low to medium altitude, seldom up to 1,000 m or 1,200 m. The limit is dictated largely by the severity of frost in winter.
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Lost Crops of Africa: Fruits, Volume III Low Temperature Marula grows and bears best in warm to hot subtropical to tropical climates, but (when leafless in winter) can tolerate light frosts. Young trees are more susceptible to frost damage, but even mature trees can be badly damaged by air (“screen”) temperatures of −4°C, but it will grow in favored locations in areas with heavy frost. High Temperature This is a heat-loving crop, remarkably tolerant of high temperatures. No visible damage was observed when summer temperatures rose to 45°C in Israel’s blistering Arava Valley. Soil Swampy soils do not suit this species. Other than that, though, marula occurs on a wide range of deep, well-drained sites from sand to loamy sand to sandy clay (usually sandy loam). Acidity does not seem to be a problem: Analysis in Botswana showed the soil under 13 trees to be pH 4.7-5.5. Nor is alkalinity a problem: marula can become dominant on basalt or dolerite soils in parts of the eastern Kruger National Park. In Israel, the trees showed high tolerance to irrigation with brackish water (EC 32 dS/m).
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Lost Crops of Africa: Fruits, Volume III