A traditional marula festival in northern Namibia. Photo ©2008 PhytoTrade Africa

The Marula Tree and Its Distribution

The marula is a medium to large deciduous tree, 15 to 20 meters tall, with a wide crown and characteristic silvery, mottled bark, which peels in disc-shaped flakes.^6,7,8 The small dark-red flowers are unisexual; although widely described as a dioecious species, female flowers occasionally occur among the male flowers of a few otherwise male trees⁹ and are found in fragrant clusters at the end of the branches. The compound leaves are grey-green in color throughout the growing season, after which the tree is denuded of leaves; the end-branches are characteristically thick and erect, like upturned fingers (digitaliform).

The marula tree is in the same family (Anacardiaceae) as the mango (Mangifera indica), cashew (Anacardium occidentale), and pistachio nut (Pistacia vera). The plum-sized marula fruits are covered in a soft, leathery, pale green-yellow exocarp, which encloses the juicy translucent white flesh.¹⁰ The fruit has an exotic flavor reminiscent of grapefruit and a distinctive scent similar to pineapple.¹¹ The fruits usually fall to the ground in large numbers while still green, where they ripen to a yellow color. They develop a pleasing resinous fragrance when on the tree and even more so when ripened.¹² Over-ripe fruits begin to ferment spontaneously. The smooth skin is tough and leathery, protecting an edible white fibrous flesh that is tart and juicy. Within the fruit is a large very hard seed, which contains one to three edible kernels, rich in edible oil.

. Photo ©2008 PhytoTrade Africa

The genus name (Sclerocarya) is derived from the Greek for hard (skleros) and nut (karyon). Marula or morula (Afrikaans) is the local name for this tree. Marula has many names in local languages, including toa (San), iganu (Ndebele), onganga (Ovambo), morula, merula (Pedi), mapura (Bechuana), umGanu (Swazi), tsua (Tonga), ol-mangwai (Maasai), umganu (Zulu), and omuongo (Herero). Marula trees are distinctive for their exceptional fruit and nut yields. In heavy fruiting seasons, a single tree can provide between 21,000 and 91,000 fruits,¹³ making them very easy to harvest. The prolific nature of the marula tree has not only been noted by humans, but also by elephants that travel considerable distances to gorge themselves on the fruits.¹⁴ Importantly, the marula fruit harvest season occurs between January and March at the beginning of the school year, making the cash income from their sale in informal markets or through more formalized market channels important for the payment of school fees and clothing.¹⁵

Marula trees are widely distributed throughout the tropical and subtropical zones of the African continent, with the subspecies caffra (Sonder) restricted to southern Africa. The tree usually grows at medium to low altitudes in frost-free areas, on sandy soils, or on sandy loams. Marula’s drought resistance makes it ideally suited to Namibia, Botswana, Zambia, and Zimbabwe, where it is found in abundance. In these places, it is one of the few trees left standing after wild bush-veld and savannah are burned and cleared for subsistence agriculture. The marula is of great economic importance to rural communities and every part of the tree, from the leaves to the roots, is utilized for a wide variety of domestic needs (See Table 1). In southern Africa, the edible fruits are consumed locally and are also used to make beer, wine, and jam.^6,16 The bark, roots, and leaves are used in traditional medicine to treat diarrhea, diabetes, fever, and malaria.^6,17 The leaves are used to make a relish and the hard wood makes excellent mortars for pounding corn, as well as spoons and other kitchen utensils.⁶

. Photo ©2008 PhytoTrade Africa

The tree has vital subsistence value in times of drought and famine.¹⁸ Wherever marula grows, it is venerated and conserved by Africans for the abundance and reliable harvest of its fruit; for generations it has been customary to parcel out rights over these trees among local inhabitants.4,16,19

Local Production of Marula Oil

The extremely hard seeds of the marula tree are difficult to crack without crushing the kernel, and specially designed small implements are used to open the opercula or “eyelets” in the seeds to pry the kernels out. Archaeological evidence confirms that the marula tree and the production of oil from its kernels has been a central part of the way of life in southern Africa for thousands of years.^1,21,22 There has been speculation that endocarp material recovered from archaeological deposits aged at 150,000 years in Zimbabwe shows significant resource usage around the time that Homo sapiens was emerging as a species. There is wider acceptance that much younger material (9,000–11,000 years old), from the same area near Bulawayo in Zimbabwe, reflects the earliest organized exploitation.^10,22 Archaeologists have also found marula seeds at Mapungubwe, where Boskopoid people lived over 1,000 years ago. Specially shaped pieces of bone, typical of Iron Age sites in the Transvaal, were possibly used to crack marula seeds.^6,23 Similar tools are used to this day to crack the seeds and extract the kernels, and it is likely that the modern uses for the tree have been passed down the generations from Stone Age Homo sapiens.

Processing marula kernel. Photo ©2008 PhytoTrade Africa

The nutritious oil and protein-rich kernels (See Tables 2 and 3) are processed by women for both domestic use and sale.^24-27 They are extracted manually from the seeds using a range of techniques specific to different parts of the trees’ distribution range (See Table 3). On the sandy coastal plain of the Ingwavuma district in KwaZulu-Natal Province in South Africa, decortication is achieved by cracking the seeds against a stone slab and removing the kernels individually with a sharp needle-like tool.²⁸ In parts of Namibia, the marula seeds are cracked against an axe blade or other large piece of iron using a block of hard wood. In Bushbuckridge in Mpumalanga Province, and some other areas of South Africa, the seeds are boiled or heated in a fire prior to decortication. This is said to make extraction simpler as the “eyelets” in the seeds are removed more easily.²³ The kernels are so full of oil that a squeeze with the hand can release a rich yield. The oil is traditionally prepared by squeezing it from the kernel in a mortar and pestle or by crushing the marula seeds and kernels in boiling water so that the released oil floats to the top of the water and can be skimmed off. Oil and cake prepared in this way can be stored and used for at least a year.

The fact that many rural households in southern Africa are in need of extra income to improve living conditions, contributes to peoples’ positive perception of the commercialization of marula. They use the money for basic needs such as food, school fees, and hospital expenses.²⁹

Marula kernels. Photo ©2008 PhytoTrade Africa

Traditional Use of Marula Kernels and Oil

Marula kernels and oil make an important contribution to the diet of many rural African people in Mozambique, Namibia, South Africa, and Zimbabwe.^30,31 It also plays an important role in the diet of the San (the indigenous people of the Kalahari desert in Botswana and northern South Africa).³² The kernels have also been reported to provide sustenance on long journeys. Men walking from Tzaneen in Limpopo Province to the diamond mines at Kimberley in Northern Cape Province take marula kernels mixed with millet meal in a large horn, slung over their shoulder, as the only sustenance for the long journey.⁶

A traditional marula festival in northern Namibia.. Photo ©2008 PhytoTrade Africa

The oily kernels are eaten as nuts, fresh or roasted, or stamped to form a cake which can be eaten on its own. The cake is occasionally used to feed animals.^{1,6,9,14,26,33-36} The kernels are also pounded or ground into powder that is added to sauces, soups, and other foods, such as biscuits and porridge.^{6,10,37,38,39} The kernels have a delicious flavor and are regarded by many indigenous people as the “Food of Kings” because of the hard work required to obtain even a small quantity from the hard seeds.⁴⁰

Due to their high fat, protein, and mineral content, the seeds provide a valuable emergency food during seasons of food shortage.^16,28 Krige reported that marula seeds were once an important staple food in drier regions of the Limpopo Province of South Africa and that in Mpumalanga Province of South Africa, the Phalaborwa ethnic group (which is locally regarded as a “Marula culture”) subsisted largely on the stored nuts during the winter dry season.¹ Similarly, Cunningham showed that on the Maputaland coastal plain in KwaZulu-Natal Province, the nuts are still stored and provide a major source of protein during drought periods.²⁸ Marula kernels have also been used as a famine food in Zambia and Tanzania.

Depending on the extraction process used, marula oil has been shown to have good free radical scavenging properties attributed to a non triglyceride fraction (which varies from 3,800 to 4,300 mg/ kg). Research into the identification of this fraction is ongoing.

Containing high proportions of oleic acid as well as 4% to 7% linoleic fatty acid, marula oil is easily absorbed, making the oil potentially useful for topical application. Marula oil has also been shown to improve skin hydration and smoothness, and it also reduces redness.⁴⁸

Preliminary tests to investigate the commercial potential of marula oil as an ingredient in cosmetic formulations have been successfully carried out (See Table 6). In vitro tests included skin hydration, transepidermal water loss, and “increase in skin smooth

Lucy Welford, PhD, is the marketing and communications Manager at PhytoTrade Africa. Welford has been working in community-based natural resource management in southern Africa for 16 years and holds a doctorate in geography from the University of Cambridge in the United Kingdom.

Maria E. Abad Jara is an environmental scientist with an MSc in environmental technology. She works for PhytoTrade Africa as a researcher. Jara’s work focuses on the development of the natural products industry in southern Africa, exploring the traditional uses, properties, and commercial viability of indigenous species.

Nigel Gericke, MD, is a physician, botanist, and consultant in the fields of natural products innovation, and natural products scientific and medical affairs. He is the co-author of the books Medicinal Plants of South Africa (Briza 2002) and People’s Plants: Useful Plants of Southern Africa (Briza 2000). He is also head of ethnobotany at Esperanza Medicines Foundation in Switzerland, managing director of HG & H Pharmaceuticals (Pty) Ltd., and a director of Niche Botanicals (Pty) Ltd.

PhytoTrade Africa, the Southern African Natural Products Trade Association, is a nonprofit entity dedicated to the development of a viable and enduring natural products industry in southern Africa, based on resources accessible to poor rural communities. With over 50 member organizations in 8 countries, its objective is to deliver large volumes of sustainably-harvested natural products, thus providing many small-scale rural producers with access to markets and an equitable livelihood alternative.

Since 2003, PhytoTrade Africa has been working in partnership with Aldivia, a specialist French lipids company based near Lyon that produces innovative natural and organic cosmetic ingredients and derivatives. Both partners share the belief that together they can make a difference in the lives of people in Africa and their environment.

After extensive research and development, the partners have developed the Ubuntu line of African natural lipid oils. Seven virgin African oils, including marula, have been subjected to a unique process that has been developed to maintain oxidative stability and antioxidant properties while at the same time complying with the stringent microbiological and toxicological quality specifications required for international skin care formulations. PhytoTrade and Aldivia are both signatory to a charter that expresses their commitment to Fair Trade, organic, environmental sustainability, good governance, and best practices. Aldivia and some PhytoTrade Africa members are organically certified through Ecocert and both partners are working towards Ethical BioTrade biodiversity verification. Aldivia has developed Ubuntu oils under ISO guidelines. No Fair Trade standards as yet exist for these oils, but PhytoTrade Africa is in ongoing negotiations with Fairtrade Labeling Organizations International (FLO) to develop standards.