Brachylaena discolor

DC.
Family: Asteraceae
Common name:
Coast silver oak (E), Kusvaalbos (A), Phahla (Z), Mphahla (N.So), umPhahla (X)

 

Seed heads

Brachylaena discolor is a very decorative shrub or small to medium-sized tree, an excellent hedge plant and is particularly useful for stabilising dunes.

Description
Brachylaena discolor forms a dense, wide, spreading, single or multi-stemmed tree that branches low down to form an irregular v-shaped canopy. The trunk reaches 45 cm in diameter and is covered with light brown fibrous bark. The trunk is divided into several large branches that tend to grow upwards and then horizontally to form bows. In the garden this tree grows to a height of 4-10 m but can reach up to 27 m in a forest.

LeavesThis fast growing evergreen has a silvery-blue appearance from a distance so that it stands out amongst other vegetation. The attractive and unusual foliage characterizes this tree. The leaves are simple, large (5-11 cm long x 1,3 cm wide), leathery and glossy dark green above and covered with a silvery-white felt of dense hairs below. The margin is distinctly toothed in young leaves and irregularly toothed in older leaves. The leaves are elliptic with rounded tip and narrow base and are spirally arranged towards the ends of branchlets and twigs. The movement of the wind through the tree exposes the lovely silver undersides of the leaves.

Masses of nectar rich creamy-white flowers are grouped in 7 to 50 flowered heads, and the heads are grouped together in large terminal panicles. These thistle-like flowers grow at the ends of branchlets. The male and female flowers are borne on separate trees. Flowering season is during winter-spring (July to September), and when in flower, the entire tree is covered in flowers. Being nectar rich they attract bees, birds and other insects that come to feed on the nectar or on the insects attracted by the nectar.

The seed is a small nutlet in a brown capsule that is tipped with yellowish, paintbrush-like hairs, and is ripe in summer (November to January).

Distribution
Brachylaena discolor occurs in coastal woodland, bush and on the margins of evergreen forest from the Eastern Cape to Mozambique. It is also very common and easy to find in the dune forests of the coast, where it grow in groups, and in the low-lying, sand and scarp forests of the coast, along rivers and in woodland of the bushveld-savannah. Its natural inclination is to form a dense bushy shrub.

Derivation of the name
The silvery grey foliage of this tree and its coastal habitat give it its common name of coast silver oak, although it bears no actual relationship to oaks but the foliage probably reminded the early settlers of an oak. The genus name Brachylaena is from the Greek brachus meaning short and klaina, a cloak and refers to the short floral bracts surrounding the disc. The specific name discolor, is Latin and means having two different colours and refers to the two colours of the leaves i.e. glossy dark green above and silvery grey below.

Brachylaena discolor is one of the few tree species belonging to the well-known daisy family, the Asteraceae. This genus consists of approximately 15 species that occur in Africa and the Mascarene Islands, and 9 species can be found in southern Africa.

Medicinal and cultural uses
The wood of Brachylaena discolor is yellow, durable and very strong and is used in the manufacture of boats at it lasts well in water, as well as for fence posts, huts, axles, spokes, implement handles, knobkerries, and long straight branches used to construct roofs of huts. Suitable branches also make excellent fishing rods, and fire shades are also made from this wood. The wood is extensively used for carving purposes by Kenyans, where it is regarded as the best wood after African black ebony. The leaves are very bitter and unpalatable and are occasionally browsed by nyala, bushbuck, red and blue duiker. Both Africans and European settlers used the leaves for medicinal purposes to treat kidney conditions. The leaves were used by country folk to make remedy for diabetes. The Zulu people used an infusion of the roots as an enema to stop bleeding of the stomach and an infusion of the leaves as a tonic to treat intestinal parasites and for chest pain. The ashes of the tree were used by early settlers to provide the alkali needed in soap making. The roots and stems were used by Zulu diviners to communicate with their ancestors. Brachylaena discolor is an excellent bee tree and is popular with beekeepers as it makes good honey

.Silvery -blue appearance

Growing Brachylaena discolor

Brachylaena discolor is fast and easy to grow and its striking foliage makes it an asset in any garden. In a garden situation, it reaches a height of 4-10 m and has a non-invasive root system, thus making it ideal for coastal gardens, parks and schools. The coast silver oak tolerates pruning and coastal conditions and makes excellent hedge or windbreak and is often used to stabilise dunes. It is drought- and frost resistant and will grow well in shade or full sun. It grows best in sandy to loamy soils and makes a good container plant.

Brachylaena discolor can be propagated from heel cuttings taken during spring. The cutting material is best treated with a root stimulating hormone, like Seradix no. 2, and placed in tray filled with a medium of 50% bark and 50% polystyrene. Cuttings are placed on a mist bed and rooting can take place from 6 weeks onwards. Plants can also be propagated from seed sown in spring or summer.

References

  • Palmer, E. 1977. A field guide to the Trees of South Africa. Collins, London & Johannesberg.
  • Keith, Paul and Meg Coates Palgrave. 1985. Everyone's guide to Trees of South Africa. C. Struik, Cape Town
  • Esterhuyse, N., von Breitenbach, J. and Soghnge, H. 2001 Remarkable Trees of South Africa. Briza, Pretoria
  • Palmer, E. and Pitman, N. 1972. Trees of Southern Africa. A.A. Balkema, Cape Town
  • Grant, R. and Thomas, V. 1998. Sappi tree spotting Kwazulu-Natal, Coast and Midlands. Jacana, Johannesberg
  • Jackson, W.P.U. 1990. Origins and Meanings of Names of South African Plant Genera. U.C.T. Printing Dept., Cape Town.
  • Leistner, O.A. (ed.) 2000. Seed plants of southern Africa: families and genera, Strelitzia 10. National Botanical Institute, Pretoria

Norma Jodamus
Kirstenbosch national Botanical Garden
January 2003



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