Shea may not be well known in a global sense, but it certainly is well known in West Africa. There, it constitutes the principal useful tree in a band of savanna nearly a thousand kilometers long. Traditionally, this large and treasured species, not unlike oak in general appearance, provided the primary edible vegetable fat to peoples inhabiting an estimated 1 million km2 of wooded grassland. Early travelers observed that the cultures in that vast area—which collectively extends through 13 of today’s countries, from Senegal to Sudan and Uganda—revolved around shea.1 One such traveler was Ibn Batuta, who passed through in 1348; another was Mungo Park, the first European to trace the inland flow of the Niger River, in 1796.
Although few outsiders have heard of it, shea (pronounced “shay” or “shee”) remains among West Africa’s most extensive resources. All told, an estimated 500 million specimens of fruiting age exist, which probably equals the number of almond trees worldwide. The tree’s fruits resemble large plums or very small avocados. The smooth-skinned, egg-shaped nut found at their center contains a kernel that yields the fat, which is widely used for cooking or for food. Indeed, West Africans use it much like Westerners use lard and butter.
This lipid is not liquid like a common vegetable oil. Rather, it is solid. Even in the tropical heat its texture ranges from a creamy paste to something like firm butter. A well-made sample taken from fresh nuts is white, odorless, and nearly tasteless.
It is difficult to overstate this vegetable fat’s importance to the inhabitants of the semiarid zone below the Sahara. For millions living in this harsh location, where food is difficult to produce and life hard to sustain, shea butter is vital to everyday existence. It enhances the taste, texture, and digestibility of the major regional dishes. It is, for example, added to the staple known as tô—mainly to prevent that pasty porridge’s surface from drying out but also to add flavor and consistency. Shea butter is also used when frying fritters, griddlecakes, and many other foods for use in the home or for sale in the markets.
Beyond shea butter, this tree produces edible fruits, edible flowers, medicines, and several other necessities. And it does it all without human help or horticultural support in some of the most challenging inhabited sites on earth.
For all its international obscurity, shea is clearly very important. It is often the principal economic resource over extensive areas where little else saleable can be found or grown. It is the main profit center for the poor.
Throughout the Sahel, shea provides poor people cash. A survey in Burkina Faso indicated that the nuts provide 20 percent of family income, a figure that can be taken as generally representative of several neighboring nations and parts of nations. The Sahelian countries can hardly be called prosperous, of course, but without shea they would be much poorer. In Mali, field studies indicate that in areas where the shea is widespread 90 percent of the households engage in its processing, and that shea products contribute up to 60 percent of women’s income. In years of poor production local market activity in notably affected.
Women are the ones who collect shea nuts. Women also extract shea butter. And women selling the butter in local markets are a commonplace sight. According to estimates, the tree provides more than half women’s income in the rural Sahel. An observer has estimated that these nuts provide income to more than 2 million women, which is in all likelihood an underestimation.2
This tree also provides the Sahel with foreign exchange. Both the seed kernels and the butter are shipped to Europe and Japan, and now the United States, where they are processed into baking fat, margarine, cocoa-butter substitutes, and various beauty aids. Such exports have a long history. In Cleopatra’s time, for instance, caravans bore clay jars of shea butter across the Sahara to Egypt where it was used in cosmetics, probably including those the queen herself applied. Since at least those dynastic days, shea exports have been providing West Africa with revenue. Currently Burkina Faso and Mali, which together ship over 100,000 tons of dried kernels annually, are the principal exporters. But shea is also an important Ghanaian export. Indeed, it’s Ghana’s third ranking cash crop; only cocoa and coffee exceed it in foreign exchange earnings. It is Burkina Faso’s third largest export as well.
Although renowned for the food it provides, this tree’s non-food products are valuable too. Across West Africa, shea butter is applied to the skin and hair. Refined in modern factories, it is incorporated into soaps, ointments, and skincare products of numerous kinds. It is also used to waterproof the walls of houses, so as to stop the infrequent downpours from washing the mud away. Furthermore, it is a staple of West African medicine. For thousands of years local healers have used the pasty solid to protect small wounds, heal infections, and soothe the aches of sprains and strains. Moreover, they prescribe it as a decongestant and an arthritis treatment.
People are not shea’s only beneficiaries. This tree’s environmental contributions are hard to overstate. For one thing, shea and locust (Chapter 11) commonly provide the only tree-cover across an area that is vulnerable to desertification. (the main zone of areas threatened with desertification is
north of where the shea is principally found; however, shea is primarily responsible for helping to prevent wind erosion and adding organic matter back to the soil). Its importance in this regard is locally understood. Laws forbid anyone from destroying a shea, and in most West African countries a person found felling one is prosecuted. As a result, shea trees are traditionally preserved during land clearing and farmers guard and tend the existing specimens, many of which are privately owned.
Perhaps it is no wonder this single species ends up forming pure stands often hundreds of hectares in extent. But beyond the solicitude of people and governments lies a probably more important reason: the thick and spongy bark. This covering is fireproof and it protects shea trees from the periodic blazes that incinerate other species.
Because of these natural and manmade protections much of the grassland below the Sahel is more like grassy woodland.3 Shea turns it into a sort of park, commonly with as many as 20 to 25 mature trees per hectare savanna. Moreover, much of it is a farmed park and is in fact a creation of human selective pressure over generations. Shea are protected and other species culled out. This is one of the most widespread and striking examples of traditional agroforestry associations found anywhere on the planet. People plant their crops among the trees. Shea combines well with cereals; farmers usually protect their trees with great care. Even though anything casting shade on a crop reduces yields, research indicates that in the short run the value of shea products more than compensates for the lost production, while in the long run the soil-saving services conferred through the trees presence may far exceed any yield losses. This time-honored farm/park landscape covering major portions of the Sahel is a perfect example of large-scale agroforestry. The dispersed trees form an integral part of the normal cropping system and have done so for centuries, if not millennia.
A self-reliant tree species that provides food in the dry, drought-seared savanna would seem the ultimate in sustainable agriculture. Making the most of the difficult climate and the most of the largely worn-out soil, the trees need no care and may live several centuries.
But these upbeat points constitute only one side of the shea story. Based on its benefits shea may seem exceptionally promising, but that does not mean that overnight it can turn into a miraculous new resource. For this, there are several counterbalancing and discouraging reasons.
First, it is far from easy to build a bigger and better shea industry because the current trees are all wild. As a result, they are widely scattered and their yields vary up and down from year to year. A steady harvest can therefore never be relied on.
Second, this species has so far proven recalcitrant to research. It has been
called temperamental and awkward and has only recently, for instance, been brought into plantations like oil palm or olive. Indeed, getting the shea tree to the point of formal cultivation presents so many challenges that both mainstream science and modern industry have largely passed it by.
Over the last 50 or so years there have been sporadic attempts to establish plantations, but in the past none was ever followed through to a successful conclusion. Indeed, only now do they seem commercially promising. For that, there is a simple explanation: The trees are very slow to mature. Moreover, the search continues for regular-fruiting varieties that can be relied on to yield fruit consistently year after year. It is little wonder, therefore, that many researchers basically gave up on this species. Most concluded that large-scale plantings would never be viable. In their frustration, they dubbed the shea tree “untamable.”
Third, the production of shea butter remains mostly a cottage industry, which restricts its size and reliability. Worse, it is a process so onerous that to produce a liter of butter requires eight hours of very hard labor. Indeed, it takes so much time it must be put off until the dry season when not even farm chores can interfere.
The traditional process as used by Sahelian women is especially tedious. During the month or two in which the fruits are ripening, they visit the trees almost daily to collect any fallen ones before others or animals get to them. They set the fruits aside to ferment. Once the pulp has rotted a bit and the seed inside has separated, they remove the seed, wash it, and usually lay it in the sun to dry. Alternately, some seeds are dried, either by a briefly roasting in an oven or boiling followed by sun drying. Once they’ve been heated and dried this way, the seeds can be safely stored. They are also easily shelled to release the kernels inside. In the main processing step, those kernels are crushed or finely ground and heated once more. The resulting hot brownish mash is then churned and strained and kneaded for hours until the white pasty fat emerges.
This lengthy and exceedingly tiresome operation is done almost all by hand. Processing shea seeds is so laborious as to almost defy economic sense. Furthermore, poverty often compels women to sell their shea products to agents who then sell them on to exporters, who in turn sell them to the international food or cosmetic industry. The women—without whom shea products would be unavailable—thus profit little from their weeks of hard labor. One estimate of the maximum value of shea butter production per family per year was US$35. Even as grower cooperatives show increasing promise, old marketing patterns remain difficult to overcome
In sum, then, the shea tree is an enigma.
And the trends in modern times are making it ever more enigmatic. Following this long period of research neglect, consumers worldwide are discovering shea products for the first time and are demanding more. For one thing, food industries are finding special uses for shea butter in pastries
(where it provides high dough pliability) and confectioneries (where it acts as a substitute for cocoa butter). Shea butter is also becoming a worldwide base for cosmetics and for treating such things as dry hair, dry skin, burns, and general dermatological ailments. The Internet is already overpopulated with peddlers pushing this newest skincare wonder.
Clearly then something needs to be done about this crop. Not only is the international demand rising, but the people living where shea grows are among the poorest and most desperate on earth. Any product capable of earning them an income and earning their countries foreign exchange is a critical resource.
Thus, despite abandonment by previous researchers and claims that the tree is untamable, action to advance shea production must be renewed. And it is finally happening. Some development agencies and many NGOs, focusing especially on women’s issues, have initiated innovative programs. Some seem to be showing great promise, but scientifically almost everything remains to be done. Though shea butter (of highly variable quality) is appearing in many products worldwide, especially cosmetics and balms, no one—least of all the present writers—has a full grasp on exactly what all to do.
As noted, in the past few years the importance and potential of shea has drawn the attention of several government and nongovernment organizations, as well as commercial enterprises—especially as shea butter has become a premium ingredient in skin emolients. Appropriately, much of this work has been developmental rather than research; the journey is just beginning toward understanding this outstanding plant. In the Next Steps section below, we present some possible lines of investigation that could lay the foundation of a greater, more reliable, and more profitable resource— one that helps the people and the land, both of which are among the most defenseless on earth.
A holdover from the ancient times, shea butter is a still-unbroken link between the hunter-gatherer and agricultural civilization. But whether it finds an even greater place in the 21st century will still depend on raising and regularizing its production. How, when, and where shea will end is therefore more guesswork than judgment. It is even possible that shea will achieve a lesser place in this new century. The trees are being subjected to pressure from agriculture, drought, and a parasitic plant that sucks out their lifeblood. Shea butter production may actually decline in coming years. On the other hand, the prospects for greater production should rise as applications in the cosmetic and pharmaceutical industry develop. That would make shea butter commercially more desirable and it would not only give more cash to the producers but also more incentives for even greater development.
Humid Areas Probably poor. Shea is not known in locations where rainfall and humidity are high…but the reason behind that is not known either. Although the tree might possibly thrive under good rainfall, it seems unlikely that it would be a viable resource in any location where oil palm, other oilseeds, or cacao grow well.
Dry Areas Fair to good. This is the climatic zone where the tree finds its greatest prospects of course. Any tree that can provide resources in this hot, dry, exasperating locale would be welcomed. In this case, though, it is only in the dry areas of West Africa that it holds reasonable commercial promise. Parched locations in East and Southern Africa should try another crop if they want any commerce to eventuate.
Upland Areas Poor or limited. Shea grows at an altitude of 1,200 m in Cameroon, but most African highlands can find more reliable alternatives for producing the kind of products this tree yields.
Commercially speaking, shea is probably not yet worth trying. Even if it will grow well in a non-African setting, the combination of matching the climate, long lead-times for production, and processing challenges may keep shea at a competitive disadvantage outside Africa.
The nuts and the butter tend to be used for different purposes when exported than when used locally. In Europe, for example, the fat is prepared by mechanical means and is used as a cooking fat, as a raw material for manufacturing margarine, and as a substitute for cacao butter in such things as chocolate and cocoa and used in cosmetics. The press cake or extracted meal ends up as cattle feed.
Below, we highlight the age-old West African uses.
Fruits The sweet, yellow or green pulp of the fruits is eaten when fresh. It is not unlike avocado and provides a valuable food during the early part of the rainy season, a time when other eatables are often scarce. Each tree typically produces 15 to 20 kg of fruit.
Seeds The kernel found within the walnut-like seed (that lies at the heart of the fruit) is, as we’ve said, the tree’s major product. The kernels can be eaten fresh or roasted like almonds. The typical shea tree’s annual yield of 15 to 20 kg of fruit corresponds to 3 to 4 kg of kernels or 1.5 to 2 kg of fat.
But the traditional methods of extraction recover only about half that. In other words, 4 kg of kernels generally yield less than 1 kg of shea butter.
Flowers The outer whorl of sepals (the calyx) is edible and is eaten especially in salads.
Shade The shea’s spreading crown is much appreciated for the coolness it throws. In the torrid locations where this tree grows, people and animals both cherish its shade above almost everything else.
Wood The wood is hard and red in color. It reputedly resists termites, and finds various applications as a utility timber. For one thing, the wood is renowned for making tools. For another, it is used for coffins. In fact, it was the traditional material for ancient kings’ funeral beds, carved from the wood of a noble old shea tree—a fact indicative of just how intimate and long the relationship between humans and shea has been. The wood makes good charcoal and fuel as well, although, because of its high value as a food, the tree is not felled for burning, even where fuel is in high demand.4
Cosmetic Uses Countless Africans use shea butter for cosmetic purposes, and these days the product is going global. Indeed, it is touted on the Internet as the only moisturizer or emollient a person could ever need. It has a mild, pleasant smell and combines well with essential oils for any desired fragrance. According to the breathless advertising, shea butter is the ideal treatment for dry, damaged, or aging skin and hair. Proof is lacking, but the possibility this is the truth seems real to users.
Medicinal Uses As noted, shea butter is locally used in medicines. It is particularly valued in ointments for boils and skin diseases. Despite a dearth of controlled experiments, it seems to enhance the healing of small wounds, cracks, crevices, and ulcers in the skin. Reportedly it contains no known allergens and is used even around the eyes. The tree’s roots and bark have separate medicinal applications, which are less well documented or trustworthy. In addition, the wastewater from processing kernels is often used as a pesticide against weevils, apparently with good effect.
Other Uses Shea butter is said to be “the ideal treatment for drumheads.” In addition, the leaves and young sprouts serve as forage. Although the foliage’s palatability is said to vary greatly with the tree and the location, livestock generally like it. Sheep and pigs also eat the sugary pulp of any fruits that have fallen to the ground. The flowers yield nectar for bees. As
mentioned earlier, shea butter is daubed to waterproof mud walls. Most often, a coat of the fat is applied seasonally around the dwelling’s doors and windows as well as along the base of the outer walls.
Nutritionally speaking, this tree is noteworthy for providing a storable food that can provide a steady source of dietary energy year-round. Shea butter is made up mainly of triglycerides. Two fatty acids predominate: oleic (unsaturated) and stearic (saturated). The average fatty-acid composition has been given as: oleic, 40 to 55 percent; stearic, 35 to 45 percent; palmitic, 3 to 7 percent; linoleic, 3 to 8 percent; and linolenic, 1 percent.
Whereas the fatty-acid composition of shea and cocoa butter are fairly similar, shea butter has a much higher content of unsaponifiable matter, up to 17 percent unsaponifiables (8 percent on average). This non-fat fraction is composed of phenols: tocopherols, triterpenes (alpha-amyrin, lupeol, butyrospermol, parkeol), steroids (campesterol, stigmasterol, beta-sitosterol, alpha-spinasterol, delta-7-avenasterol), and hydrocarbons (2-3 percent karitene). It also contains terpenic alcohols.
Strictly speaking, there is no such thing as shea horticulture. After all, there are no operating plantations. However, where people have tried planting the trees they have commonly employed a regular grid pattern with 10m x 10m spacing.
Shea seeds germinate easily when fresh but lose this ability quickly. The seedlings grow a long taproot, which endows great drought resistance, but makes them difficult to transplant. Seeds are therefore perhaps best planted in situ. Trees raised from seed mature very slowly, bearing their first fruits after 12-25 years and taking 30-50 years to achieve full productivity.
In principle, vegetative propagation could reduce that delay and lift the crop’s potential in many other ways. So far, though, it has not been accomplished on any scale. This is an exciting time in shea propagation. Success with cuttings has been achieved, though methods presently seem challenging except with good skills and facilities. Grafting, though difficult and often inefficient, also works if practiced carefully. Air-layering has also been successful, yet it too has proven difficult to pull off reliably in practice. In vitro propagation is also reported. Just which methods to recommend are uncertain as of now; practitioners and decision-makers are advised to start first by searching the Internet and then consulting experts before making any long-term commitments.
In the wild, the tree sends up root suckers, a propensity probably providing the easiest way to produce shea vegetatively for small-scale commercial purposes. One researcher has recommended laying root sections (about 15 cm long and up to 1 cm thick) in nursery beds or large pots. After about two years, the resulting plants can be moved into the field. Although slow, this procedure is free to the local grower, and may remain the best method to increase planting material until elite selections become more widely available and reasonably priced.
Shea suffers from few diseases but some insect pests and four parasitic mistletoes (Tapinanthus sp.) cause it great—even mortal—damage.
HARVESTING AND HANDLING
The fruit is allowed to fall naturally from the tree and is collected from the ground. This occurs during the rainy season. Yields vary considerably. A harvest of 5-15 kg of nuts (kernels with shells) per year per tree is said to be average, but harvests up to 45 kg from trees that were protected and well-tended have been recorded.
Shea butter is extracted using several variants of the basic traditional method. The procedure used by the Mossi of Burkina Faso can be taken as representative: The freshly collected fruits are placed in pits and kept moist for several days to ferment. After the loosened pulp has been pulled off, the
nuts are cleaned, boiled or roasted, and dried. They are then pounded and crushed to break off the hard brown shell and expose the kernel (or “almond”). Shaking and winnowing the mixture, as if it were grain, removes the particles of broken shell. The kernels are then air-dried to approximately 10 percent moisture, at which point they neither germinate nor decompose and can be safely stored for months without spoiling.
Next comes the main task. The dry kernels are heated over an open fire until they start “weeping.” This exudation of oil means they have reached the temperature at which the solid fat liquefies: 38°C. The hot kernels are
then poured into a mortar and pounded using a heavy pole or flat rocks. This task is so long and so onerous that several women generally share the burden. The result is a reddish-colored paste. After cooling, this paste is rolled-out flat so the bigger impurities can be picked out. The fatty residue is then poured into a vessel and alternately rinsed in hot and cold water. Finally, it is kneaded, cooked in an iron pot, and steadily kneaded again with a rhythmic tumbling action until a white layer of fat rises to the surface. This “virgin” shea butter is skimmed off and wrapped tightly in leaves. This first-run, top-quality product may be stored for a long time. The rest is either reprocessed or discarded. Even such incredibly toilsome efforts recover only 36-40 percent of the fat in the kernels.
Of course considerable quantities of the kernels are also handled using modern methods. In Europe, especially, shea kernels are extracted using the expensive machinery designed for mass-processing other oilseeds: continuous screw press, filter press, and/or hydraulic presses. Industrial-scale extraction recovers at least 80 percent of the kernel’s fat.
Uncertainty over the harvest is certainly a prime limitation. Shea tends to bears fruit once every two or three years. In any year, two trees in three may produce almost nothing.
African mistletoe already affects a large portion of the shea population, including almost all of Burkina Faso’s trees.
As has been shown, the fat is terribly difficult to refine. Making things worse, the nuts contain latex, which clogs filters and other machinery parts. Solvent extraction is also difficult, as the latex prevents the solvent from penetrating the mass. To reduce latex problems the nuts must start out bone dry, something not easy to accomplish in a village during the rainy season.
If not thoroughly purified, the fat goes bad. The decomposition begins in the fresh nuts. These are naturally low in free fatty acids when they fall from the tree, but if handled improperly they quickly turn rancid. It is recommended that freshly harvested nuts be boiled an hour (to denature the fat-splitting enzymes) and then dried in the sun.
Since the 1940s and 1950s relatively little solid research has been undertaken on shea until recently. Many aspects remain poorly understood. In spite of its local and national economic importance, modern data on how best to produce it and its foods is still hard to come by. Further research is needed on virtually everything but, thankfully, much is at-last already underway. Though many of the challenges listed below may take years to resolve, anyone seeking answers today should first consult information and experts via the Internet.
Basic Aspects of the Tree The tree’s biology and physiology are still very uncertain. To mention just one example, shea corymbs (the fan-shaped, flower clusters) carry several dozen flowers, but as far back as 1948 it was reported that only 2 to 4 of those flowers are fertile. Studies of pollination and reproductive biology could possibly point the way to increasing fruit production many fold and perhaps regularizing the annual yields as well.
Experts have yet to find the reason behind shea’s irregular fruiting cycle. It seems probable that the bush fires and the hot dusty wind called harmattan contribute to the flowers and buds dying prematurely. Drought may also play a part. However, none of these is sufficient explanation in itself. There probably is a fascinating physiological explanation still awaiting discovery.
Basic research on the influence of climate and soil on the tree’s productivity, growth, and unreliable bearing is needed as well.
Propagation Fresh seed germinates readily but viability declines significantly within a week or so unless the seed is cooled. The deep-rooted seedlings can be difficult to establish if transplanted. There has been some success with air-layering and grafting of superior clones, as well as tissue-culturing, but more experience is needed before standard practices are fully developed and acceptable. One special difficulty is the long period needed to reach fruiting age. Traditionally, shea was believed to take about 20 years to bear fruit, with full production only reached after about 50 years! Although experience generally bears out long lead-times, well-tended trees on a plantation at Sapone in Burkina Faso bore fruits after a dozen years. Whether such substantial differences are genetic or environmental requires further study, as it has significant bearing on prospects for domestication and non-seed propagation. There is also high yield variability among different trees, so further identification and propagation of selected germplasm is of high importance. The Cocoa Research Institute of Ghana has started one such a program, but it is a very long-term process. Vegetatively propagated materials may eventually reduce initial fruiting to only a year or two.
Regeneration of Parklands The only way to stop desertification across the Sahel is to protect the vegetation. Clearly, with its widespread presence and fire-proof trunk the shea should be in the forefront of any effort to slow, stop, or reverse the expansion of the Sahara effect. At the farm level, the low-performance individual sheas could be replaced over time or reworked by grafting on branches from high-performing trees. In addition, fallows could be seeded with quality planting materials. Additionally, means such as vetiver-grass hedges or fertilizer or pest controls could be applied to regenerate trees existing in the parklands.
Although shea has occupied the savanna parklands for millennia, the tree densities over the last few decades have declined in many places. Drought,
population pressure, and landuse change have killed some and decreased the regeneration of others. However, probably the greatest concern is the very high level of parasitism by the four mistletoes (Tapinanthus species). These parasitic plants are hard to combat. Approaches that have been suggested include herbicide control, physically removing the parasite from infected trees, killing the birds that pollinate mistletoe and disseminate its seeds, and boosting the populations of bird species that eat those particular seeds that land in the top of a shea tree. These and other possible methods need to be tested for safety and effectiveness, and quickly turned into practical controls.
Food Technology Traditional methods of extracting shea butter cannot meet today’s needs, let alone tomorrow’s. Researchers have identified several easier and more efficient ways to handle the nuts and still produce good quality butter locally. Although improving, these do not yet live up to their full promise, and continued diligent effort is sorely needed. Local production is crucial for a reason beyond local consumption: Africa exports more than 10 times more butter in seeds than as finished product, thus losing all that potential value-added profit
Using machinery to reduce the human drudgery is clearly necessary. This is not a novel notion. Mechanized shea processing has already been introduced to West Africa. Some uses sophisticated technology, some “appropriate technology.”5 Mainly, these approaches have involved mills to crush and grind the nuts, but there have also been attempts to use centrifuges to process the butter better and solar driers to dry the nuts. Solar technology has become very popular in West Africa, and solar driers are an especially intriguing possibility to ease handling the fresh kernels. This, as well as perhaps other techniques, would reduce the possibilities of the nuts decaying when they are stored in their shells, increase the efficiency of roasting and boiling the nuts, remove the tedium of extracting the oil, increase the recovery rate of the fat, and improve the storage qualities as the shea moves from savanna to salon.
Horticultural Development The current average production per tree is estimated at about 10 kg of fresh fruit. Clearly, this could be increased. A tree the size of an oak should be capable producing much more, and up to 200 kg has indeed been reported. Particularly good trees are well known and greatly prized in certain locations. Now is the time for a registry, so seed and cuttings can be collected and the production of quality plants for mass use made possible.
Overall “superiority” is not an easy thing to pin down, however. It might be based on the nut (the number, size, and butter quality, for instance). It
might be based on the pulp (weight and sugar content, maybe). It might be based on the tree’s growth characteristics. Individual trees with early, lengthy, or semiannual flowering may be of over-riding value for improved overall production. As standards are determined, the heritability of such production characteristics from superior trees raised through seeds also deserves study.
Arguably, the greatest of all research needs is vegetative propagation. This needs further research improvement, because it permits ready multiplication of superior trees. Perhaps the main problem behind all the vegetative methods is the plant’s latex, which literally gums up the grafts. This is common to trees of this family (Sapotaceae). Indeed, another member of the family is sapodilla (Manilkara zapota), which is the original source of chewing gum. Sapodilla and sapote (Pouteria sapota) are commercially grown in tropical America. The special techniques developed for those latex-filled relatives might help open new possibilities for shea. Tissue culture should also be more widely explored, although here time-to-maturity once again becomes an issue, as does the added possibility of genetic off-types only revealing themselves after years of growth and investment.
There is also need for garden-variety horticultural research. With shea the possibilities for individual contributions are great. For instance, management of seedlings and trees needs improvement, and the use of mineral and organic fertilizers for faster growth and better fruiting deserve assessment.
Increasing Output At least in theory, production could be vastly increased in one simple way: collect more of the nuts. Presently, the natural wealth of the shea tree is not fully exploited, and much—even most—of the wild crop goes unharvested each year.6 There are an estimated 94 million shea trees in Mali, for instance. Theoretically, therefore, that country alone could produce 80,000 tons of nuts a year, which could transform its economic standing in the world.
In this regard, more knowledge is needed on land tenure and how the tree rights are distributed among household members and community groups. This is important because new processing technologies and new market opportunities will make the crop more valuable, and inevitably lead to conflict over the trees’ ownership. Research should be conducted to anticipate the consequences, good and bad, particularly to the traditional users, notably women. In many places, it may be simply that available labor is insufficient when the nuts fall, and simple techniques—manual or mechanical—that are used with other plants to collect “windfalls” may close
The cause is also partly economic. Current prices do not encourage farmers to fully utilize this resource. Demand and price are strongly influenced by the availability and cost of other vegetable fats, especially cocoa butter, so the price is not always controllable. Because of this and other factors, many harvests must be sold when local prices are low. Indeed, the women mostly sell on a seasonal basis, when the markets are already flooded with shea butter. Possible answers may include producer cooperatives, direct marketing, and shea-storage facilities. The small producers would then at least earn more money.
Product Research According to some observers, shea’s future depends on developing uses for its unsaponifiable matter. This non-fat part of the seed displays several interesting physical and biomedical properties that could have pharmacological and cosmetic applications. These higher-value uses include prevention of skin drying, the soothing of sore skin, protection and lubrication, fast release and long retention of active ingredients, and high UV absorption.
Further research is therefore needed on the properties and applications of the unsaponifiable matter. Recognition of shea butter’s unique properties and applications could result in big price increases at the point of sale. In theory, higher profits would then encourage capital investment in its production. And that could help fund research to make shea a booming resource for the whole Sahelian region.
Botanical Name Vitellaria paradoxa C.F. Gaertn.
Synonyms Butyrospermum paradoxum, Butyrospermum paradoxicum ssp. parkii, Butyrospermum parkii, Lucuma paradoxa (Gaertn.) A. DC
Arabic: lulu, sirreh (Chad)
Bambara: se, berekunan, tamba
Burkina Faso: taanga (moore)
English: shea, shea butter, butternut tree, bambuck or galam butter
Dioula: karité (“life”)
Ghana: sukpam (Frafra); nku or ngu (Ashanti); yokumi (Volta)
Hausa: mai, k’danya, bagay
Peuhl: kare, kolo
This is a stout tree that can grow up to 20 meters tall with a trunk over a meter in diameter. It is deciduous, but never looks it because the new leaves arrive at the same time the old ones fall. The crown is dense and many-branched; its shape very variable. In adult trees, the bark is dark, thick and deeply cracked into squares, like crocodile skin. The leaves are tough and strap-like, mostly clustered at the ends of branches. There is an extensive root system, essential to help the tree survive the seasonal or multi-year droughts of the savanna climate.
The brownish or creamy-white flowers are also mostly clustered at the ends of branches. They seem pollinated by insects, mostly bees. The fruits ripen during the early rainy season. They are spherical or ellipsoid berries 3-6 cm long, borne on a stalk (peduncle) 1-3 cm long. The pulp is yellowish-green and sweet.
The nut at the center of the fruit consists of a thin brown shell enclosing a single, dark-brown, egg-shaped kernel, inside which is the fatty substance known as shea butter. The nuts are about 3 grams in weight. Sometimes they contain more than one kernel.
Within Africa Shea occurs in the southernmost parts of the Sahel and the adjacent Sudan and Guinean savannas. Senegal is the western extent of its range.8 Dense stands are found from Guinea through Mali, Burkina Faso, and Niger. The trees also occur in Guinea Bissau, Sierra Leone, Côte d’Ivoire, Ghana, Togo, and Benin as well as Nigeria and Cameroon. East of this region, there are scattered occurrences across Central Africa from Chad through Sudan to far-western Ethiopia, Uganda, and Congo.
Beyond Africa The tree is, as far as we know, unknown outside Africa except for a report from Honduras, where it is called “tango.”
Although elite single specimens are known and reproduced by seed, and provenance trials of vegetative material are underway, there seem to be no
true-to-type varieties. The species itself has been divided into two subspecies, subsp. paradoxa and subsp. nilotica. The former is found at lower altitudes (up to 600 m and occasionally much higher, but always west of the Nile drainage basin), is more drought-resistant, and takes longer to sprout (up to five months).
Shea grows in the dry forests and savanna with a very marked dry season of 6-8 months. There are also periodic droughts that go on several years. It also occurs scattered in dry forests throughout the Sudano-Sahelian zone, but does not extend into coastal areas. It is a light-demanding species of open sites, mostly solitary, and over its principal ranges commonly forms pure stands.
Rainfall Shea is found in areas with 400-1,800 mm rainfall per year. However, the trees are most common and healthy where they receive 600-1,200 mm and where the dry season lasts no more than 8 months.
Altitude Shea grows generally at low altitude, although on Cameroon’s Adamaua Plateau it ascends to 1,200 m above sea level.
Low Temperature It grows in areas characterized by average annual temperatures of 24-32°C. The minimum is reported to be 21°C.
High Temperature Temperatures where shea is found commonly climb into the lower 40s.
Soil Shea occurs naturally on the dry slopes of the savanna zone, but not in alluvial hollows or land subject to flooding. It is found on various soil types but seems to prefer dry and sandy clay soils with a good humus cover. Nonetheless, it tolerates stony sites and lateritic subsoils, although its yields may not be great.