| Common name | Winter Thorn, Anna Tree |
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.