General Info

This unarmed Tree is up to 15m high.  The bipinnate Leaves have elliptic leaflets.  Whitish, zygomorphic, 5-merous Flowers are in pendulous spikes.  Fruit is a thin indehiscent pod with 1 Seed.

Description

Burkea africana

RSA Tree No. 197.

Common names: Red Seringa, White Seringa, Wild Seringa, Seringa tree.

Family: Fabaceae, 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 include Acacia (Vauchellia, Senegalia), Albizia, Bauhinia, Bolusanthus, Burkea, Calpurnia, Colophospermum, Cyclopia, Dichrostachys, Erythrina, Erythrophleum, Faidherbia, Indigofera, Mundulea, Peltophorum, Philenoptera, Schotia and Xanthocercis.  The Fabaceae are recognisable by their fruit and by their pinnately compound Leaves.  Leaves may also be simple 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: Burkea – named after Joseph Burke (1812-1873) a widely travelled plant collector and hunter in the RSA from 1840-1842.  His trip is worth reading – see ref.  africana – from Africa.  This is the only species of the genus Burkea in southern Africa.

Conservation Status: L C. (Least Concern).  2009 (Raimondo et al.).

Tree

This unarmed, flat-topped or rounded crowned Tree is 10 to 15m high.  The Trunk may reach a diameter of up to 80 cm.  The Bark is rough, dark grey, fissured and often flaking.  Green lichen may be present.  The inner bark is either pink to dull red or purplish brown.  The ends of young branches are broad, rusty-red to maroon and have densely matted hair (photos 1053 and 174).  This is a distinctive feature – especially in winter.  Roots can extend horizontally for many metres and are generally shallow.

Leaves

The Leaves are crowded at the ends of branches and tend to droop.  They are bipinnate (Compound: twice pinnate.  The central axis or rachis has lateral “branches” not leaflets and the leaflets are on these side pinnae “branches”).  Each leaf consists of 2-3 pairs of pinnae and each pinna has 4-9 well-spaced, alternate Leaflets.  Each grey-green, blue-green to dark green leaflet is roughly elliptic and up to 6 x 3cm.  The terminal leaflet is not centrally placed.  Old leaves are often marked with brown spots.  Only young leaves have silvery hairs that lie tight against the blade.  The Apex is rounded or notched and the Base is asymmetric.  The Margin is entire (with a continuous margin, not in any way indented). The Petiole (leaf stalk) has a swollen base and is up to 10cm long.  Petiolules (stalks of leaflets) are short.  Glands are lacking.

Flowers

The bisexual, creamy-white Flowers are crowded towards the ends of branches.  They may appear before or with the new leaves.  They provide a white, mat-like mass.  The flower buds are green-yellow.  Flowers are small – up to 5mm wide and arranged in attractive pendulous Spikes (simple indeterminate inflorescence with sessile flowers on a single unbranched stalk).  These spikes are up to 24cm long.  The Bracts (modified leaves associated with reproductive structures like cone scales and inflorescence axis) are small and are persistent until the flowers open.  Individual flowers are zygomorphic (irregular flower: when corolla is divisible into 2 equal halves in one plane only).  The Calyx is campanulate (bell shaped) having a short tube with 5 rounded lobes.  The lobes are longer than the tube and are valvate (meeting by the edge without overlapping).  The 5 free, imbricate (with overlapping edges) Petals are obovate-oblong and up to 5mm long.  There are 10 nearly equal Stamens and each is about 5mm long.  The Anthers have a sessile apical gland.  A single Pistil (a unit of the Gynoecium, the female element of the flower, composed of the Ovary, Style and Stigma) is present.  The superior partially sunken Ovary is densely hairy.  It has a short, thick Style and a funnel-shaped Stigma, which is slit down one side.  (Sep-Nov).

Fruit

The pale brown, thin, coriaceous (leathery), flattened, elliptic, Fruit is an indehiscent Pod that is up to 8 x 2,5cm.  The stipitate (supported by a short stipe or a short stalk) pods, which are wing-like, hang in clusters that mature by July but may remain on the tree for months.  Each pod usually holds one compressed Seed.  The tree may only produce fruit every second year.

Distribution & Ecology

These Trees are often found in deep, sandy soil in deciduous bushveld (a sub-tropical woodland ecoregion of southern Africa).  They occur in different woodland types from 50 to 1 700m.  They grow naturally in Gauteng – common round Pretoria, Limpopo, North West, Mpumalanga, Mozambique (mainly central and north), Northern Namibia, Botswana and northward towards Ethiopia and Nigeria.  This plant does best with annual rainfall from 1 000 to 1 200mm.  Larvae of the butterfly Apricot Playboy (Deudorix dinochares) feed on the Leaves.  Elephants eat the Branches and leaves and monkeys eat the Flowers and Pods.  Porcupines eat and may damage the Bark.  This tree is often associated with other trees including Terminalia sericea, Ochna pulchra, Colophospermum mopane, Pterocarpus angolensis and Combretum imberbe.  Although initially susceptible to fires, mature trees tend to recover well after the passage of a fire.

Ethnobotany

The dense hard Wood is pale yellow to yellowish brown.  The sapwood must be treated to prevent borer attack.  The wood is lustrous and takes a fine polish.  It saws easily but has a marked cross-grain, which makes it difficult to plane.  It does not shrink much and has good gluing properties.  Nailing may cause splitting and pre-boring will help overcome this.  The Heartwood is used for fence posts, parquet flooring, railway sleepers, mortars and attractive furniture.  The centre of the bowl is often defective.  Wood is used as a Fuel.  Caterpillars of the moth (Cirina forda), which have a wingspan in excess of 10cm, consume the Leaves.  These caterpillars also provide food for the local people.  They are boiled and lightly roasted and may also be dried and stored.  Leaves may be toxic to stock.  Bark contains alkaloids and tannins and extracts can be used for tanning.  Dried, crushed bark is used as a fish poison.  Seeds are difficult to cultivate and trees are slow growing.  Roots provide a red dye.  Twigs show antimicrobial activity against a wide variety of bacteria and fungi – supporting the use as a chewing-stick for dental care.

 

References

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

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.

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

 

http://redlist.sanbi.org/species.php?species=239-1

http://www.africanmoths.com/pages/SATURNIIDAE/SATURNIINAE/cirina%20forda.htm

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

https://en.wikipedia.org/wiki/Burkea_africana

http://prota4u.org/protav8.asp?p=Burkea+africana

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

https://everipedia.org/wiki/Joseph_Burke_%28botanist%29/