General Info – summary

This graceful Tree is up to 12m high with deeply grooved mature bark.  The imparipinnate Leaves have paired lanceolate leaflets.  The blue, pea-like, bisexual, zygomorphic, 5-merous Flowers are in racemes and each has 9 joined and 1 free stamen.  The single pistil has a superior ovary with a single curved style and a capitate stigma.  The flat, papery Fruit is a brown, tardily dehiscent pod with leathery seeds.

Description

Bolusanthus speciosus  

Previous Names: Lonchocarpus speciosus.

SA Tree No. 222.

Common names: (Afr) Olifantsboom, Olifantshout, Vanwykshout.  (Eng) Elephant Wood, Elephant’s Wood, Rhodesian Wisteria, Rhodesian Wisteria, South African Wisteria, Tree Wisteria, Wild Wisteria.  (isiZulu) Umhohlo.  (Northern Sotho) Kgomo-nahlabana, Mogapa.  (Setswana) Mosôkaphala, Motsokophala, Nsukungaphala.  (siSwati) Umhohlo.  (Tshivenda) Mukamba, Mukambana, Muswinga-phala.  (Xitsonga) Mpfimbahongonyi, Npfimbahongonyl.

Family: Fabaceae or Leguminosae. (Pea, bean or legume family).  After the Orchidaceae and the Asteraceae, the Fabaceae is the third largest Angiosperm (flowering plants) family with 700+ genera and close to 20 000 species.  Local Tree genera on this website include Acacia (Vauchellia, Senegalia), Albizia, Bauhinia, Bolusanthus, Burkea, Calpurnia, Colophospermum, Cordyla, Cyclopia, Dichrostachys, Erythrina, Erythrophleum, Faidherbia, Indigofera, Mundulea, Peltophorum, Philenoptera, Piliostigma, Schotia and Xanthocercis.  The Fabaceae are recognisable by their fruit and by their pinnately compound Leaves.  Leaves may also be simple – even bilobed and usually have stipules – some of which may be spinescent.  Leaflets are usually entire.  Flowers are bisexual and bracteate.  Regular flowers usually have 4-5 sepals and the same number of petals.  Irregular flowers have 4-5 sepals and 5 or less petals.  Stamens have anthers that have 2 pollen sacs and there are usually at least twice the number of stamens as petals – often 10.  The superior Ovary has one locule that may contain 1 or more ovules.  The Stigma and Style are simple.  The single carpel develops into the Fruit, which is usually a pod.  This pod dehisces on both sides and may break into segments.  Seeds vary.

Name derivation: Bolusanthus named after the founder of the Bolus Herbarium in Cape Town: the Englishman Dr Harry Bolus 1834-1911.  He was a botanist, a botanical artist, businessperson and philanthropist.  Five genera carry his name.  speciosus – spectacular / showy / beautiful – referring to the flowers.  Bolusanthus speciosus was first collected in Mozambique and is the only species in this genus.

Conservation: National Status: L C. (Least Concern).  Assessed: 2005 (W. Foden and L. Potter).

Tree

With its normally narrow Crown, this impressive single trunked Tree is usually up to 6m high but may reach 12m+.  The Trunk is usually straight and, when multi stemmed (photo 238); the stems remain straight but emerge at an angle (photo 239).  Young branches are light to dark brown or grey and here, fallen leaves leave visible leaf scars.  Mature Bark is rough and deeply longitudinally fissured (photos 225 & 228).

Leaves

The shiny Leaves tend to droop and are located towards the ends of branches.  Each reasonably opposite leaf is imparipinnate (compound leaf ending in a single leaflet – photos 250 and 227).  It contains between 3 and 7 pairs of leaflets and the single terminal one.  The Petiole (leaf stalk) is up to 1,3cm long and has a thickened base (photo 227).  Each distinct Petiolule (stalk of leaflet) is about 0,5cm long.  Stipules (basal appendages of the petiole) are present.  It usually holds its leaves until just before the flowers open and the emergence of the new leaves (photo 250).  Young leaves are a silvery-bronze (photo 250).  Mature leaves are a bright shiny green above, lighter and a duller green below.  On a sunny day, minute silvery hairs on the upper surface make the leaves visible from a distance.  The lanceolate Leaflets are jugate (having leaflets in pairs – each attached to the single leaf rachis -photo 227).  Each leaflet measures up to 7 x 1,6cm.  Lateral veins may be yellowish and are slightly more visible below.  The Margin is minutely scalloped (photo 017 – observe carefully).  The distinctive Midrib is pale yellowish and protrudes slightly below (photo 017).  The Apex is narrowly tapering, and the Base is markedly asymmetric causing the leaflets to curve (photos 017 & 227).  This tree may be briefly deciduous.

Flowers

The impressive, violet to pale blue Flowers develop in large, (up to 30cm long) pendulous inflorescences called Racemes (simple elongated inflorescences with stalked flowers).  They arise before or with the new leaves and may almost cover the tree (photo 868).  The individual scentless 5-merous (having a specific number of parts) flowers are pea-like, bisexual and zygomorphic (irregular flower with the corolla divisible into 2 equal halves in one plane only).  The Calyx has 5 Sepals (photo 933) with the 2 uppermost joined high up.  The Corolla has 5 Petals.  The largest upper petal (standard or vexillum petal) stands vertically outside the rest.  It is much broader than other petals and has an impressive, distinctive white patch in its centre (photo 921).  Below this are the pair of lateral petals – the wings.  At the base, there are 2 joined keel petals which are as long as the wing petals.  There are 10 Stamens (photo 503) of which 9 have joined filaments and the tenth, uppermost one, is free.  The white Filaments may have attractive blue dots (photo 503) and bend sharply upwards near the end to place the Anthers perpendicular to the ground thus aiding pollen dispersal in the process.  The versatile (hung or attached near the middle, and usually moving freely), elliptic anthers are a golden colour – at least initially.  There is a single Pistil (a unit of the Gynoecium, the female element of the flower, composed of the Ovary, Style and Stigma).  Here the superior Ovary with up to 8 ovules extends into a single curved Style which ends with a small capitate (shaped like a head) Stigma.  (Aug-Dec).

Fruit

The belatedly dehiscent Fruit is a narrow, pointed, flat and tardily dehiscent Pod.  It is up to 9 x 1,2cm and has up to 8 seeds.  The flattish dry pods are papery and hang down (photo 230).  They usually turn light brown but may age to dark brown or black.  The remains of the Calyx are still visible on the maturing pods (photo 228 & 17 – under Leaves).  The leathery Seeds resemble those of beans (photo 228) and cause the pods to bulge slightly.  In this photo, the remains of the style are just visible at the end of the pod.  (Oct-Mar+).

Distribution & Ecology

The Roots are non-invasive and do well in clay soils.  This Plant is common in wooded grassland, at low to medium altitudes and in savanna (a rolling grassland scattered with shrubs and isolated trees, which can be found between a tropical rainforest and desert biome).  They occur naturally in North West, Limpopo and northern Mpumalanga along the foothills of the nearly 130km long W-E Soutpansberg mountains.  They also occur in KwaZulu-Natal, Gauteng, Eswatini (Swaziland), Mozambique (mainly central and south), Zimbabwe, Botswana, Malawi, and Angola and are thus endemic in southern Africa.  Vervet monkeys eat the flower buds.  Monkeys, gemsbok, giraffe and grey duiker eat the Fruit and Leaves.  Guineafowl overnight on the branches (photo 217 – under Trees).  Scale insects may infect the tree and their presence causes small bumps on plant stems.

Ethnobotany

The Wood is one of the best of our indigenous trees. It is hard, heavy, easy to work on a lathe and is termite and borer resistant – making it useful for fence poles.  Hoe, axe and pick handles, fence poles and furniture are made from it.  In the early days, wood was used to make wagon wheel spokes.  The sapwood is white, and the heartwood is reddish.  It grows best from shallowly planted seeds in hot sunny, dry areas and grows slightly less than a metre per year but does not transplant easily.  Protect young trees from frost and do not water excessively.  This is a spectacular tree when flowering.  Bolusanthus speciosus is a protected tree in South Africa.

References

Boon, R. 2010. Pooley’s Trees of eastern South Africa. Flora and Fauna Publications Trust, Durban.

Burrows, J.E., Burrows, S.M., Lotter, M.C. & Schmidt, E. 2018. Trees and Shrubs Mozambique.  Publishing Print Matters (Pty) Ltd.  Noordhoek, Cape Town.

Bryant, C. Lombo, B. 2004. Trees of CC Africa. Double Story Books, Cape Town.

Foden, W. & Potter, L. 2005. Bolusanthus speciosus (Bolus) Harms. National Assessment: Red List of South African Plants version 2020.1. Accessed on 2022/12/22.

Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.

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. Jacana, Johannesburg.

van Wyk, B. & van Wyk, P. 1997. Field guide to Trees of Southern Africa. Struik, Cape Town.

 

http://www.plantzafrica.com/plantab/bolusanthspec.htm

http://www.zimbabweflora.co.zw/speciesdata/species.php?species_id=127280

http://posa.sanbi.org/flora/browse.php?src=SP