Vachellia hebeclada subsp. hebeclada
Vachellia hebeclada (DC.) Kyal. & Boatwr. subsp. hebeclada
Common names: candle thorn (Eng.); trassiebos (Afr.); mohae (S. Sotho)
SA Tree No: 170
This beautiful shrub to small tree is the most common naturally occurring vachellia in the Free State National Botanical Garden. It may reach up to 7 m in height, branching from near ground level and is often wider than high, occurring generally in hot, dry areas, often forming thickets.
Its growth form can vary considerably. Over large parts of its distribution range it occurs as a prostrate, spreading, multi-stemmed shrub with dense branches near ground level or with stems rising from branching underground stems. In this form it may be no more than 1 or 2 m high, but can achieve a diameter several times its height. In appearance it is thus often reminiscent of a large, flattened cushion. In some areas it occurs as a more upright shrub or small tree 3 to 8 m high with rounded, spreading crown and drooping branches, also with a considerable horizontal spread. As a low shrub it is found in dry savanna and grassland areas and on soil ranging from Kalahari sands to sandy alluvium soils, often associated with calcrete. As a more upright shrub or tree it is usually found on more moist soils with higher clay content. It is considered to be a good indicator of calcium-rich soils. It is fairly tolerant of cold.
The bark on the main stem of the tree form is thickened, dark brown to grey and longitudinally fissured, giving the stem a striped appearance. In the prostrate form the bark on the numerous main stems is dark and fairly smooth. Young, new season's shoots appear light grey due to a dense cover of short whitish hairs, and they have a velvety feel. Older, previous season's shoots are smooth, hairless, olive green to reddish brown with light-coloured transversely elongated lenticels. Still older shoots have grey bark, peeling to reveal an orange to reddish brown colour.
The stipules are modified into hardened, spinescent spines and occur in pairs at nodes. Their size and shape vary considerably. Large spines are mostly straight with only the tips slightly recurved, while shorter spines may be strongly recurved. They are usually borne at right angles to the stem, but can be raked backward or forward.
The leaves are borne at the nodes, singly or up to 4 leaves per node. The petiole and rachis are light green, grooved on top and hairy. The leaflets are bluish green with spreading hairs on the margins. A petiolar gland, if present, is fairly large and located near the junction of the first pinna pair. There is a small raised gland at the junction of the distal 1-3 pinna pairs.
Inflorescence: globose flowering heads are borne at the nodes, either singly or in groups of up to 8 per node on both new season's and previous season's shoots. The colour of the developing buds is green prior to full bloom. The open, fully developed flowering heads have a diameter of 13-17 mm. They are scented and are pale yellow to cream. Peduncles are hairy with a length of up to 20 mm. The involucel is small and located just above the base of the peduncles.
Pods and seeds: the pods are quite large and very distinctive. They are borne at the nodes on stout stalks and stand erect. They are straight or nearly so, tapered at the base and rounded at the tip. The pods are tardily dehiscent (opening spontaneously), only splitting partially. They can contain up to 10 seeds. The seeds are reddish brown, roughly elliptic and thickened, with a size of 6-15 x 4-11 mm. With its characteristic prostrate growth form and distinctive straight spines with recurved tips it is unlikely to be confused with any other South African Vachellia or Senegalia species, especially when the large upright pods are present.
Distribution and habitat
This tree is widely spread in the northern provinces of South Africa
Derivation of name and historical aspects
Hebeclada refers to the pubescent (hairy) branches. Vachellia refers to George Harvey Vachell (1789 – 1839), chaplain to the British East India Company in Macoa, who collected plants in China. This plant was previously called Acacia hebeclada.
The flowers of Vachellia hebeclada attract lots of small insects like bees and flies which cross-pollinate them when moving from one to the other. This vachellia is called "a house of the lion" as lions shelter in it.
Farmers should note that under certain conditions some species of Vachellia are poisonous. The trassiebos, Vachellia hebeclada, more often a shrub than a tree, is also reported to be poisonous. In all cases the poison took the form of prussic acid.
Growing Vachellia hebeclada subsp. hebeclada
Seed is set freely and, being little affected by parasites, can be collected without difficulty. The thickish testa needs filing and seeds should be brought to the boil and then left to soak for some 24 hours before being sown. Seeds germinate in 5 to 8 days, a reasonable proportion germinating if the seed has aged sufficiently. In amplification, it may be pointed out that seed of subsp. hebeclada, gathered in spring and sown in mid-August gave very poor results, while with seed collected in December from the same plant and sown in that month, a fair proportion germinated.
- J.D. Carr. The South African Acacias. Published by Conservation press (Pty) Ltd. Johannesburg.
- Keith Coates Palgrave. Trees of Southern Africa in association with R.B. Drummond Edited by Dr E.J. Moll, new edition revised and updated by Meg Coates Palgrave.
- Eve Palmer F.R.H.S and Norah Pitman. Trees of South Africa
- Nico Smit. Guide to the Acacias of South Africa, first Edition, published by Briza Publications. Pretoria.
- Kyalangalilwa B, et al. 2013. Phylogenetic position and revised classification of acacia s.l.(Fabaceae Mimosoideae) in Africa, including new combinations of Vachellia and Senegalia. Botanical Journal of Linnean Society 172,500-523.
Free State National Botanical Garden
Plant Type: Shrub, Tree
SA Distribution: Free State, Gauteng, Limpopo, Mpumalanga, North West, Northern Cape
Soil type: Sandy, Clay, Loam
Flowering season: Late Summer
PH: Alkaline, Neutral
Flower colour: Green, Cream
Aspect: Full Sun
Gardening skill: Average