This Tree with tough spines on the branches may reach 15m high. Wood is hard and dense. Simple Leaves are hairless. Tiny, greenish, 5-merous, unisexual Flowers are in cymes. Fruit is an orange drupe.
Chaetacme aristate, Chaetacme madagascariensis, Chaetacme microcarpa, Chaetacme nitida, Chaetacme serrata.
RSA Tree No. 43.
Common names: Thorny Elm, Basterwitpeerhout.
Family: Ulmaceae. This family of 9 genera and 45+ species – at the moment. Species includes the elms – in the genus Ulmus. Members have leaves and bark with mucilaginous substances. Leaves are simple, and may have an asymmetrical base. They are often alternately arranged. The small Flowers are bisexual or unisexual and lack petals. The indehiscent Fruit may be a drupe, nut or samara. Local genera include Chaetacme.
Name derivation: Chaetacme – referring to the bristle tipped leaves. aristata – bearing a long bristle-like point (referring to the leaves). Chaetacme aristate is the only species in southern Africa.
Conservation Status: L. C. Least Concern. 2009 (Raimondo et al.).
Description: This Tree that may reach 13m high and produces a dense canopy. Tough, straight Spines occur on branches. They may be paired and are more numerous on coppice (if young tree stems are repeatedly cut or burned down to near ground level this may cause regrowth from the stump or roots) branches. The plant may also be a vigorous shrub that may scramble. The Stem (main axis of the plant, the leaf and flower bearing as distinguished from the root-bearing axis) may be fluted. The Bark is pale grey. Branches may occur low-down. Branchlets (a small branch or division of a branch – especially a terminal division; usually applied to branches of the current or preceding year) tend to zigzag between nodes. These young branches are initially green with longitudinally running lenticels (a usually raised corky oval or elongated areas on the plant that allows the uncontrolled interchange of gases with the environment).
The hairless thick, stiff and alternatively arranged Leaves are usually entire (with a continuous margin, not in any way indented). The leaves are up to 9 x 5cm and are thick and stiff. They are minutely punctate (with translucent or coloured dots or depressions or pits) on the lower side. Leaf shape varies between lanceolate and ovate. The blade is often widest above the central part. The Apex is broadly tapering or rounded and often notched with a hair-like bristles at the tip. The Base is slightly asymmetric. Margins are rolled under. Some may be serrate (saw-toothed margin with teeth pointing forward). The upper surface is dark green and glossy. The lower surface is lighter. Here parallel lateral veins and net veins are visible. All veins are clearly visible when the leaf is held against a strong light (photo 824). The Midrib is clearly visible on both sides and protrudes below. The Petiole (leaf stalk) is short. Terminal buds are enclosed by large, leathery Stipules (basal appendages of the petiole). They are connate (a leaf shaped as though the bases of two opposite leaves had fused around the stem) along one margin. However, they are caduceus (an organ or part of which is easily detached, and shed early). One or 2 straight Spines may occur in leaf axils.
The small greenish, monoecious or dioecious unisexual Flowers occur in cymes (a broad, more or less flat-topped, determinate flower cluster, with central flowers opening first), panicles (indeterminate, branched inflorescence with stalked flowers) or are single. Small bracts subtend flowers. Flowers lack Petals. The Perianth (the 2 floral envelopes considered together; a collective term for the calyx and corolla) has 5 deeply concave lobes with inflexed sides. Male flowers have 5 Stamens which emerge from the perianth lobes (photo 210). The Anthers are 2-thecous (2 pollen sacs) and dehisce through longitudinal slits. Pistillodes (sterile pistil in a male flower) are present. In Female flowers, staminodes are absent and 1 perianth lobe is smaller than the others. Female buds are imbricate (having regularly arranged, overlapping edges, as roof tiles or fish scales). The sessile, 1 locular, superior Ovary is pubescent (hairy). 2 hairy styles are present. There are 2 long unbranched hairy persistent Styles present. (Sep-Dec).
The thinly fleshy, almost spherical Fruit is a Drupe (a fleshy, 1-seeded indehiscent fruit with the seed enclosed in a stony endocarp; stone fruit e.g. peach) with an apical protruding remains of the stigma (photo 510). Seeds lack endosperm (the starch and oil-containing tissue of many seeds; often referred to as the albumen). (Oct-Dec).
Distribution & Ecology
The Trees occur naturally in the Western Cape – Knysna and eastwards, Eastern Cape, KwaZulu-Natal, Gauteng, Mpumalanga, Limpopo, North West, Swaziland, Mozambique, West Africa, Sudan and Madagascar. These plants occur along streams and wooded grasslands near the coast. Many animals including Nyala and Black Rhino graze Leaves. Rhino also eat the Bark. Butterflies. The larvae of the Blue-spotted Emperor (Charaxes cithaeron) and the forest king emperor (C. xiphares) butterflies, feed on the leaves. Birds. The Purple-crested Turaco (Purple-crested Loerie), and the Thick-billed Weaver eat the Fruit.
The Wood is hard, dense and tough. It is difficult to cut and not much used.
Boon, R. 2010. Pooley’s Trees of eastern South Africa. Flora and Fauna Publications Trust, Durban.
Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.
Ginn, P.J. McIlleron, W.G. Milstein, S. 1989. The Complete Book of Southern African Birds. Struik Publishers (PTY) LTD. Third impression 1991.
Lawrence, G. H. M, 1951. Taxonomy of Vascular Plants, The Macmillan Company, New York. Tenth Printing 1965.
Palmer, E. & Pitman, N. 1972. Trees of southern Africa, Balkema, Amsterdam, Cape Town.
Schmidt, S. Lotter, M. & McCleland, W. 2002. Trees and Shrubs of Mpumalanga and the Kruger National Park.
van Wyk, B. & van Wyk, P. 1997 Field guide to Trees of Southern Africa, Struik, Cape Town.