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Lost Crops of Africa: Fruits, Volume III
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Lost Crops of Africa: Fruits, Volume III 10 MONKEY ORANGES Although perhaps more than 20 Strychnos species produce edible fruits in various parts of Africa, three stand out. Strychnos cocculoides, S. spinosa, and S. pungens produce large, pleasantly flavored fruits that are easy to handle and often in short supply. Farmers appreciate the trees so much that when clearing land they spare them the ax—even if plowing or planting field crops will be awkward. These three special monkey orange trees are widely enjoyed and have the amazing capacity to stay edible in tropical heat for months after maturity. This is important for food security: monkey orange has been called, “A great and precious resource in times of crop failure.” Of all Africa’s native fruits, these are perhaps the most “conventional.” They are similar in size and shape to apple, pear, and orange trees. Given horticultural attention, they probably can be raised with equal facility. There have other advantages, too. They bear fruit in abundance. They make excellent additions to gardens, parks, streets, and fence lines, by providing not only food but also shade, shelter, and erosion protection. Above all, though, these fruits provide a profit. Indeed, they sell at very high prices and still the full demand is seldom met. A much greater commerce in monkey fruits is eminently possible. Even an export trade is not beyond question. Zimbabwe has already exported some of the fruits to Botswana, and that could be just the beginning. High prices, high productivity, great shelf life, unmet demand…these are the makings of success in any fruit. However, few people have attempted to produce monkey oranges in organized cultivation. For all intents and purposes, they remain unknown to horticulture, and remain undomesticated. Clearly, these three special monkey orange trees warrant intensive research and development. And that has begun…at least in a modest way. In southern Africa, selection and cultivation of monkey oranges is underway, in hopes these plants may eventually be grown intensively. Beyond the possibility of orchards, however, is the promise of improving production from the wild resource and expanding monkey orange trade within and among African nations. These fruits may find a home beyond Africa as well.
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Lost Crops of Africa: Fruits, Volume III One species grown in Israel is already showing enough promise for optimism about its future as a crop.1 In these three special Strychnos species, fruits tend to be yellow, orange, or brown in color and about the size of grapefruits. They are marketable size and quite stunning to the eye. They typically store and ship far better than most fruits. Indeed, they can be piled in the open for storage because their hard, gourd-like shell resists not only fungi but also fruit flies. Some are even buried several months, and (as long as the shell has no cracks) they come out of the ground juicy and golden ready for dessert.2 The yellow or brownish pulp inside the fruit surrounds a number of scattered but conspicuous seeds. To eat a fresh monkey orange you simply suck the juicy flesh from around those seeds. A particular problem with some Strychnos species is that, although the ripe pulp is safe to eat in moderation, eating too much at one time can be purgative. In addition, care must be taken not to chew the seeds of most (but not all) the species. Those smooth and shiny seeds, as well as the bark and roots, contain strychnine and may produce vomiting or headaches. Their slippery nature makes them easy to swallow accidentally, but they pass through the body safely without causing harm. However, in extreme cases, after chewing irresponsibly the bitterest seeds, even death may occur. These facts are widely known where these trees occur, and at least in Strychnos pungens not even the seeds seem to contain toxins. Although high prices, high productivity, and great shelf life make for success in any fruit, capitalizing on that promise in an organized way requires that much more be done. The priorities for domestication given in other chapters are also relevant with monkey oranges. The goal should be high and consistent yields of large, good quality fruits. And that requires technical advances such as selection, vegetative propagation, and proper management of the plants. This seems certainly achievable; however, monkey oranges have some special research needs, including: Selection of trees with minimal levels of harmful alkaloids (strychnine, bruisine) in the seeds and skins. Artificial defoliation to synchronize the fruit formation and allow orchardists to harvest the entire crop at once. Hybridization between species to explore the possibility of wholly new and perhaps exceptional fruits, al la nectarine or plumcot. This is a speculative notion, but Strychnos pungens is known to hybridize with S. innocua, so the possibility of shared genes and perhaps of seedless fruits is far from impossible. 1 Information from Y. Mizrahi. 2 An exception appears to be Strychnos spinosa, which cannot be stored for long, especially under tropical heat and humidity, perhaps because of higher fat levels.
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Lost Crops of Africa: Fruits, Volume III Stychnos cocculoides, Congo D.R. Fruits of this and the other three special monkey orange species are of marketable size and quite stunning to see. Not only are they large, flavorful, and easy to handle, they are often desperately difficult to find due to overwhelming demand. (Paul Latham) Contributor P. du Plessis summed up the overall situation: “Strychnos fruits are very popular and seldom available in surplus quantities because of an extensive local and regional trade,” he wrote on a draft. “New plantings are urgently needed to make available fruits for export markets and for processing. This should be done in Africa with Africans.” These three promising species are highlighted below. Corky-Bark Monkey Orange (Strychnos cocculoides Baker)3 This compact tree 2-8 m tall (occasionally reaching 10 m) of the Kalahari and its surrounding savannas and dry woodlands is found on sandy soils and rocky slopes in Botswana, northern Namibia, and parts of Zimbabwe and South Africa.4 It bears round fruits 6-10 cm in diameter, with hard, woody, brittle shells. When immature they look like avocados. They fall from the tree before they ripen. As they mature the thick shell turns orange, at which 3 The tree derives its name from the characteristic corky bark, deeply ridged longitudinally. It is also known as suurklapper (Afrikaans). Much additional information on this species is available in Mwamba, C.K. 2006. Monkey Orange (Strychnos cocculoides). Fruits for the Future 8. International Centre for Underutilised Crops, Southampton, UK; see icuc-iwmi.org. 4 Notably the bushveld of Gauteng (western Transvaal).
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Lost Crops of Africa: Fruits, Volume III Green monkey orange, Luphisis village, South Africa. The trees that yield monkey oranges make excellent additions to gardens, parks, streets, and fencelines—providing not only food but also shade, shelter, and erosion protection. However, fruits from these unselected trees can be disappointing as food. (Claus Lipis) point it can be broken open and the yellow or brownish pulp scooped out. The pulp is very refreshing, and its taste has been variously described as “a combination of citrus and pineapple” or “a mixture of citrus and banana.” It is much beloved. Kung people walk for days to find trees that are bearing, and fruits are widely sold in traditional markets throughout the area. They are sold, for example, in Bulawayo, Zimbabwe from September to October. In nature, the species regenerates by seed, coppice, and root suckers. The seed has a hard coat and resists easy germination. Undoubtedly, scarification techniques can be found to promote quick and uniform sprouting.5 5 Indeed, one of our contributors in Zimbabwe wrote: “I have had no trouble germinating
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Lost Crops of Africa: Fruits, Volume III In a pioneering program in Botswana, a small organization devoted to the development of wild African plant resources has made remarkable progress with improving this plant’s overall productivity. Researchers at Veld Products Research applied horticultural techniques to six superior phenotypes they obtained from the wild. Even before receiving horticultural attention those select 6 averaged between 300 to 400 fruits per tree, each fruit averaging 10 cm in diameter and a third of a kilo in weight. Those may seem like exceptional trees, but given some fertilizer and appropriate watering the fruit size rose to 15 cm diameter, the maximum production to 700 fruits per tree, and the weight to over half a kilo per fruit. Street value of each fruit (before improvement) was 40 cents in U.S. currency, so a single tree producing 700 fruits could bring in gross income of well over $200. In these trials, propagation by seed has been successful; in the nursery 80 percent germination within 3 weeks has been recorded on seeds sown in summer. (Those sown in winter took more than 9 weeks.) The plants also responded well to inorganic fertilizers.6 In field plantings at Gabane, Botswana seedlings treated with superphosphate and blood- and bone-meal (Nitrosol®) fertilizers doubled their heights (to an average of 76 cm) within 13 months, while those untreated remained below 20 cm for 3 years. Encouraging responses to grafting were also obtained. In some cases the grafted trees grew twice as fast as the ungrafted ones. They also tended to yield fruits within 3 years of transplanting. The ungrafted seedlings, on the other hand, took 4 to 5 years to bear any fruit.7 Green Monkey Orange (Strychnos spinosa Lam.)8 This small thorny shrub or small tree (6-10 m) is very similar to corky-bark monkey orange. It is, however, found more broadly throughout the drier parts of Africa: from Senegal to southern Ethiopia, and from there to the eastern seaboard of South Africa. It is a variable species, its genetic divergence being so great that three subspecies have been recognized. It is widely spread across dry tropical to subtropical savannas, open woodland, river fringes, and mountain slopes up to about 2,000 m. Although home in hot, dry tropical or subtropical savannas, it tolerates light frost. The spherical fruits—sometimes as large as a quince (15 cm in diameter)—are bright green when immature, but turn yellow when they fall, and then brown or black. They have been called “one of the best native seed from old, open fruit (presumably opened by baboons), which was thoroughly dried.” 6 Not all responded; some, for reasons unknown, stayed short and refused to flower. 7 In Zambia, however, there are reports of trees raised from seeds yielding fruits within 3 years of transplanting. Information from C. Mwamba. 8 Also known as Natal orange, monkey ball, monkey apple, elephant orange, spiny monkey orange, amahlala (Zulu), klapper, and other names. Its smooth (rather than corky ridged) branchlets help distinguish it from the very similar Strychnos cocculoides.
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Lost Crops of Africa: Fruits, Volume III fruits,” and are, for instance, one of the favorites of Mozambique, where they sell well in the markets of Maputo. The skin of the fruit is so hard it must be physically cracked open, but the pulp then comes out as a whole. It is whitish, yellow, light tan, or dark brown in color, and in flavor can be either acid or very sweet and delicate. On the tongue it can be jelly-like or juicy, and the taste is described as “somewhat like a lightly fermented tart apple, with a cinnamon-like odor that intensifies on cooking.” Although mostly eaten fresh, the pulp is used in many other ways. In Madagascar, for example, it is often cooked with cereals to form a sweet porridge or it is dissolved in water to create sweet and tasty drinks. These latter are also fermented to an alcoholic beverage. Little is known about nutritional value, but monkey oranges are reportedly rich in B vitamins and vitamin C. Tartness, as in lemons, derives from citric acid. One analysis in Malawi found it to be the highest in fat (31 percent) and energy (460 calories per 100 g) of 16 wild fruits tested, although these levels may be exceptional or anomalous, as the fruit is not normally considered oily.9 Two basic fruiting forms of this tree are distinguished. One, the so-called sweet type, has sugar-rich fruits clustered on short stalks. The other, the so-called bitter type, has long stalks, narrower leaves, and fruits that remain bitter when ripe. Although slow growing, the tree is not difficult to plant and manage, and it seems to adapt well to many types of locations.10 A well-drained soil is preferred and, despite a reputation for needing more water than other “lowveld” trees, this is a drought tolerant species. In some cases, the fruits may take several months or even a year to pass from flowering to full ripeness. They are so strongly attached that they must be cut from the trees with a knife or scissors.11 But when ripe, they fall off on their own, especially if coaxed by someone shaking the tree. The shells remain whole unless they hit something as hard as a rock, tree trunk, or each other. The seeds and bark contain strychnine and are best regarded as poisonous, although authorities differ on this point. The unripe flesh is said to cause vomiting. The rind is very bitter in taste and is to be avoided. The wood is white and is sometimes used for fence posts. 9 Saka, J.D.K., J.D. Msonthi, and J.A. Maghembe. 1994. Nutritional value of edible fruits of indigenous wild trees of Malawi. Forest Ecology and Management 64:245-248. 10 It has, for instance, been planted as a curiosity in Florida. It was introduced into Puerto Rico and Florida by the U.S. Department of Agriculture in 1921, and also into the Philippines at about the same time. 11 Pulling them off damages the tree.
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Lost Crops of Africa: Fruits, Volume III Spiny-Leafed Monkey Orange (Strychnos pungens Soler.)12 A small brittle tree, usually less than 7 m tall, this monkey orange is found from northern South Africa to Angola, Congo, and Tanzania. It often occurs where light frosts are far from unknown in winter. The fruit is round, 10-12.5 cm in diameter, and weighs as much as almost half a kilo. Like other monkey oranges, it has a woody shell, which turns from bluish-green to yellow as it ripens. The pulp is juicy, butter yellow, and has a somewhat rank odor. Although opinions about this fruit differ, some trees produce what are generally considered pleasingly fragrant and pleasant tasting fruits. The presence of citric acid makes them thirst quenching. Alkaloids are supposedly absent in the seeds of this monkey orange. This should be confirmed. The seeds are very bitter, and if consumed in quantity may cause diarrhea. Perhaps a more serious concern is the competition people face in trying to get these fruits. Not for nothing are they named monkey oranges. Indeed, the fruits are eagerly sought by monkeys, as well as by forest antelopes, or even by both together. In Natal, for instance, the miniature antelopes known as duikers commonly search under a tree for flesh enclosed seeds being dropped by careless monkeys. The whitish colored wood is hard and straight. It is much prized, especially by Zulus, who use the wood of coppice shoots for walking and fighting sticks. The species is very similar to Strychnos spinosa, and (in the absence of flowers) is distinguished by the blue-green color of the immature fruits as well as by small variations in leaf color, shape, and venation. Like other Strychnos species, this is one tough plant. It thrives from sea level to high altitude. It is to be seen in woodland, wooded grassland, and urban settings. It occurs commonly in stony places or at the base of rocky outcrops (kopjies), not to mention deep sandy soils and open woodland, riverine fringes, and coastal forests. In the harshest sites it is commonly reduced to a small shrubby shadow of itself, with many stems sprouting from the base. The seed germinates readily and reportedly the plants grow fairly fast. 12 Also known as wild orange, black monkey orange, swart klapper, botter klapper, shiny-leaved mukwakwa, and other names. According to some botanical authorities, Strychnos madagascariensis is a synonym for Strychnos innocua (or at least of Strychnos innocua subspecies dysophylla and subspecies gerrardi).