Faidherbia albida is a monotypic genus. The generic name honors Major L.L.C. Faidherbe, governor of Senegal between 1854 – 1865, who is recognized as one of the founders of French rule in West Africa.
Winter Thorn is a deciduous African tree that can grow up to 30 m tall and its roots can grow 40 m deep. It has branching stems and an erect to roundish crown. Its bark is greenish to whitish grey color and smoothness is evident on the young stems, but grey and smooth to rough on older branches and stems. The specific epithet ‘albida’ means somewhat whitish, referring to the colour of the stem.
The pale grey-green leaves are twice-compound, have a conspicuous gland at the base of each pair of pinnae (leaflets). There are 3-10 pairs of pinnae, each bearing 6-23 pairs of leaflets; leaflets quite large, 3.5-9 x 0.7-3 mm. Modified spiny stipules at the base of the leaves, thickened at the base, straight and robust 2-4 cm long. The basal thickening is a characteristic distinguishing this species from the acacias with long thorns like A. tortilis, A. raddiana etc.
Another characteristic that distinguish this species form the other Acacias is the shape of its inflorescence. About 100 scented, pale cream-colored flowers form an elongated spike up to 35-160 x 20 mm. Calyx 1-1.7 mm long, glabrous to pubescent with 5 sepals. Corolla 3-3.5 mm long with 5 free petals. Flower buds appear soon after leaves on current season's growth. It blooms during the summer months, but most flowers abort and normally 5 or less mature into pods 3-4 months later
The Winter Thorn fruit is an unusual pod, bright orange to reddish-brown, thick, indehiscent, characteristically and conspicuously curled and twisted; large, up to 25 x 5 cm. Each pod contains 10-29 dark brown, ovoid, shiny seeds each measuring 10 x 6.0 mm and separated by thin septum. The seed coat is tough, leathery and waterproof. Seeds are dispersed by herbivores eating the indehiscent pods or by the pods floating down rivers.
Faidherbia albida distribution is from Israel in the north to South African areas of Kwazulu-Natal in the south. It grows in waterlogged soils along rivers, swamps, floodplains and dry river courses. Its natural range extends throughout dry tropical Africa into the Middle East and Arabia, from 270 m below sea level in Israel up to 2500 m in Sudan. In Africa it is usually a pioneer on alluvial flats but can form part of a fire-climax vegetation in the west African savannas, where optimal conditions are between 500-800 mm annual rainfall. It withstands flooding for a number of months along the Zambezi and Nile rivers and in paddy fields.
The few isolated populations found in Israel are considered relicts form The Tertiary era of past warm-humid climate. But ancient human introduction cannot be ruled out. The Israeli populations which have been analyzed (Halevy, G. 1971 LaYaarn) genetically turned out to be clones, presumably formed by root suckers. They appear in locations of high underground water-table on a variety of soil types; on basaltic soil in Nahal Tavor, on volcanic tuff in Tel Shimron, on calcareous alluvial soils near Neve Etan, Kfar Menahem and Valley of Elah, on sandy limestone (kurkar) Netzer Sereni – Yashresh, and sand Ashdod, Nitzanim, and Zikim.
Faidherbia albida nodulates with Bradyrhizobium bacteria, common in tropical soils, and has VA mycorrhizal associations. It is important for its ability to fix nitrogen, and for erosion control. Unlike most other trees in Africa, it sheds its leaves in the rainy season; for this reason, it is highly valued in agroforestry as it can grow among field crops without shading them. The leaves from this legume tree are high in nitrogen, and can double yields in maize crops, etc., when added to the soil. Small leaflets rapidly decompose and increase the soil organic matter. There is a program planned to transplant the tree across Africa to boost production. It is maintained and protected on farms in East Africa to shade coffee and to provide shade for livestock in the dry season. The thorny branches are useful for a natural barbed fence.
Winter Thorn is important in the Sahel for raising bees, since its flowers provide bee forage at the close of the rainy season, when most other local plants do not. The pods that fall over a period of months are important for raising livestock, and are relished by elephant, antelope, buffalo, baboons and various browsers and grazers.
In West Africa pods are sometimes shaken down, collected, and fed to animals or sold in markets or at roadsides. The seeds can be boiled and eaten, but first the skin has to be removed. Also the pods may be dried and ground into flour, which is edible.
It is used for food, drink and medicine. It contains the psychoactive chemical compound dimethyltryptamine in its leaves. The extract is used to treat ocular infections in farm animals. Reported to serve as an emetic in fevers and also used for colds, diarrhea, hemorrhage, and ophthalmia in East and West Africa. Namibians use its bark for toothbrushes and is reputed to contain Fluorine.
Felled timber is susceptible to a variety of wood borers. It is used for canoes, mortars, and pestles. The wood is used for carving. Masai use it as the soft flat wood upon which the firestick is twirled to make fire. Ashes of the wood are used in making soap and as a depilatory and tanning agent for hides.
Early seed collection is recommended for propagation, to avoid heavy infestation by bruchid beetles. Hard coated seeds store well under dry conditions, and are often extracted by pounding the pods in a mortar. Pretreatment is needed for rapid uniform germination. Mechanical scarification works best for small lots. Dipping seed for 5-15 minutes in conc. sulfuric acid or covering the seed with boiling water then allowing to cool for 24 hours are also effective.
In Israel and in South Africa this tree is protected by law.
Written by Amram Eshel