Common tree of the year 2019

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Marula tree. Picture courtesy Regina Hart - see her flickr linkMarula tree. Picture courtesy Regina Hart - see her flickr link Marula, Maroela, Mufula, Ukanyi  (Sclerocarya birrea) (SA Tree No: 360)

Few African trees are held in such high esteem by indigenous peoples as the Marula, and archaeological evidence shows that it was a source of nutrition as far back as 10 000 years B.C. In the Pomongwe Cave in Zimbabwe, it is estimated that 24 million Marula fruits were eaten. However, this tree is not only cherished for its edible fruits but also for its many other uses, with almost all parts of the tree being utilised.

The Marula is a very handsome medium-sized to large deciduous tree which belongs to the mango (Anacardiaceae) family. It produces a single, sturdy, erect trunk and a beautiful rounded to spreading crown of dark green leaves. It is widespread in Africa from Ethiopia in the north to KwaZulu-Natal in the south, and is native to the following countries: South Africa, Malawi, Namibia, Niger, Botswana, Gambia, Zambia, Zimbabwe, Sudan, Swaziland, the Democratic Republic of Congo, Ethiopia, Kenya, Tanzania (including Zanzibar,) Angola and Uganda. It is also found in Madagascar, where it was probably introduced, as it was in Mauritius and Reunion.

The Marula tree is grown worldwide and is invaluable to millions of people in parts of Asia, Europe and America. It has been introduced into Australia, and is also being grown as an experimental crop in Israel. Although large trees can bear heavily, up to 70 000 fruits on a single tree, the average yield is approximately 30kg per tree.

 In South Africa it occurs naturally in the warmer, eastern parts of the continent, and is distributed in many South African game parks, and in the rural areas of Limpopo, KwaZulu-Natal, the Eastern Cape and Mpumalanga. It is more dominant in Phalaborwa in the Limpopo Province, and Mpumalanga. The Marula can be found growing in various types of wooded savannah, on sandy soils, where it usually grows about 9m tall, but under optimal climatic conditions it can reach 18m.

The trees produce sprays of small pinkish-red flowers from September to November. The male and female flowers are separated and can occur on separate trees, or on a single tree, and are pollinated by insects. The male spray is 50 to 80mm long, while the female spray is only 30mm long. Male plants produce pollen, and the female flowers produce the oval, plumb-sized fruits which start falling from the trees in large quantities from February to March. The fruit drops while it is still green and ripens on the ground, turning a light yellow colour.

The brown stone inside the fruit is walnut-sized with a thick wall and the flesh surrounding it is very fibrous and juicy, and once ripe has a characteristic turpentine flavour. Inside the stone are two to three oblong kernels, each one protected by a small bony 'lid' which becomes detached when the stone is cracked. A single tree can produce over 10 000 of these seeds or 'nuts' which are oil-rich and sought after by people and a variety of animals.

Humans find the seeds difficult to extract from the stone-like kernel, but the Cape Parrot does so effortlessly with its strong beak. Traditional healers use the hard nut in their divining dice, the Zulu crush and boil the seeds, skim off the oil and use it as a therapeutic body massage, and the Venda people are said to use the oil to preserve meat. Even the skin of the fruit is used, and is boiled to make a drink, or burnt to be used as a substitute for coffee.

The old silver-grey stems are smooth, and the bark peels off in disc-shaped flakes, giving the trunk a mottled appearance. In winter, once the leaves have dropped, these features, together with the wonderful shape of this tree, show off beautifully. The interior bark is red or pink with darker stripes. The wood is used for making many things from boats to furniture, flooring, carvings and household utensils. The inner layer of bark makes a strong rope, and a red-brown dye can be produced from the fresh skin of the bark. The tannin-rich gum is mixed with soot and used as ink.

The powdered bark is used to treat pregnant women to determine the gender of an unborn baby. If a woman wishes to have a girl, a preparation from the female plant will be taken, and for a boy she will use the male plant. A decoction of the bark is an excellent remedy for haemorrhoids, is also used to treat dysentery, diarrhoea and rheumatism, and has a prophylactic effect against malaria. Both the root and bark are used as laxatives.

Several types of parasitic plants grow on Marula trees and the larvae of eight species of butterfly feed on the foliage. Also, the larval stage of the beautiful green African moth (Argema mimosae) feeds on Marula leaves. Although various herbivores, including elephants and giraffe, browse on the leaves, it is not their most popular foliage. The grey bark of Marulas, however, is irresistible to elephants, and they can eliminate entire communities of these valuable trees through destructive ring-barking.

The Marula is a protected species in South Africa and due to its many uses is usually spared by woodcutters in most rural areas, and in the former homeland of Venda it was a criminal offence to cut down a living tree of this species. When one does see Marula trees being cut down, it is a clear indication that a community is under pressure.

Due to its well-known alcoholic capacities, rumours abound as to the Marula's intoxicating effects on wild animals, and especially since the release of a popular movie from the 1970's by Jamie Uys called "Beautiful Peope" which depicted a troop of drunken baboons under a Marula tree. Today we know through observation that game could become intoxicated after eating the fermenting fruit, however, even though baboons and elephants relish the fruit, baboons prefer fresh Marula fruit, and because the pulp and seeds are digested and passed within a 24-hour period, fermentation is impossible. And, elephants would have to eat prodigious amounts of fermenting fruit for it to have even the mildest impact, and since these huge animals drink up to 160 litres of water a day, there would also be a major diluting effect. Interestingly, examination of fresh elephant dung shows that less than ten percent of Marula fruits are actually 'processed' in any way through digestion and most fruit passes through the digestive tract intact. For these reasons it is clear that the scene in the movie was clearly man-induced, and today it would be outlawed in terms of animal cruelty.

One of South Africa's most popular locally made liqueurs called "Amarula Cream" has now become a successful export.

Health Benefits:

The abundant crop of fruit produced by the Marula is extremely high in vitamin C.

In the Kitchen:

The fruit is edible, and is eaten fresh or made into a delicious jelly or jam. The fruit is also made into beer known as "Mukumbi" by the Vhavenda people, and the sour drink is said to have "the kick of a mule!"

The delicious white nut is highly nutritious and rich in protein.  It can be eaten raw or toasted and is eaten on its own or mixed with vegetables.

Healthy cooking oil is made commercially from the kernels by a process of basic hand-pressing and filtration techniques, and no solvents are used.

Large Saturniid Caterpillars are gathered from this tree for roasting, as well as the larvae of the Cerambycid Wood Boring Beetle.

In the Garden:

The Marula is an invaluable and very attractive shade tree for large properties, farms and game farms, and in many rural fruit-farming communities a couple of these trees are planted to attract pollinators in early spring.

Cattle eat the fruit that falls to the ground as well as Marula leaves, which are nutritious and will contribute to a healthy diet for livestock. For rural farmers, using the leaves as fodder is particularly helpful during extended periods of drought when there is no grass to graze on.

Cultivation:

The Marula tree is adapted to dry and hot weather conditions, growing best in the warm, frost-free regions of South Africa. Although it is very sensitive to frost, it can be grown in areas where there is mild or occasional frost, but it must be protected for the first couple of growing seasons, or until it is well established.

It requires full sun, and grows quite quickly, with a growth rate of up to 1.5m per year. Because the Marula is found in arid and semi-arid areas with summer rainfall varying from 250 to 1 000mm annually, once established this tree is fairly drought resistant and can survive on natural rainfall. However, during prolonged drought conditions the trees will perform better if they can be irrigated. Immature specimens should be watered moderately during dry spells, until established.

The Marula is adapted to poor sandy or sandy-loam soils which drain well, so ensure that your soil also has perfect drainage. Trees can be fertilised with a general purpose fertiliser, but like other fruit-bearing trees, the quantity used will depend on the age of the tree, its health etc.

Harvesting:

The ripe fruit is collected from the ground by hand.

Propagation

This tree can easily be propagated by seed, cuttings and grafting, but vegetative propagation is preferred to seed production, because it ensures that the offspring will contain the exact characteristics of the parent material with regard to genotype and health status.

Although Marula is very easy to grow from seeds, unfortunately a seedling population tends to consist predominately of male trees. Soak the seeds overnight in warm water, and place them on damp, fluffy peat moss at room temperature for about a week or two. Plant the seed directly into black nursery bags filled with river sand and keep in a warm place in the shade until the seedlings appear. Often more than one plant emerges, but all except one plant should be removed. Transplanting should be done while the plant is still small to prevent damaging the roots - a good size is when the plant has only two leaves.

Even though shoot cutting is a propagation method, the Marula is not usually propagated by this method because of the resulting poor root system. Truncheons of 100 to 150mm in diameter and 2m long can be planted in early spring

The trees can be coppiced, regenerating rapidly, and normally farmers plant them closer together and trim the top and sides. Coppicing is the woodland management technique of repeatedly felling trees at the base (or stool) and allowing them to re-grow, in order to provide a sustainable supply of timber.

Marula trees can also be propagated successfully by means of grafting, a technique used to unite rootstocks grown in advance with selected wood cuttings from another Marula plant. The slanted cut on the graft wood and that of the rootstock must fit together neatly and the cambium layer should overlap on at least one side. Graft wood of the same thickness as the rootstock is selected and the buds must be swollen. The graft is then firmly tied with PVC grafting strip, and the entire piece of graft wood is then covered with a plastic grafting strip to keep it clean and dry until the two pieces grow together. Grafted trees have a strong root system, and are usually shorter, and bear fruit from the third to the fifth year, while seedling trees usually bear fruit in five to seven years.

Problems, Pests & Diseases:

Little is known regarding the diseases of Marula or even fungi that occur on this tree. The most important pests affecting the plant are the Marula fruit-fly, the red Marula caterpillar and the Marula beetle. Early removal and destruction of fruit-flies is recommended. To help reduce the fruit-fly population, baits can also be used to attract male flies to containers which contain pesticides.

Caution:

The information contained within this website is for educational purposes only, documenting the traditional uses of specific plants as recorded through history. Always seek advice from a medical practitioner before starting a home treatment programme.