The Tree with its thick stem has a corky bark is up 6m high. The decussate, bicoloured Leaves are large, simple and stiff. The small Flowers are in capitula. White corolla bilabiate. Fruit is a tufted cypsela.
Oldenburgia grandis, Arnica grandis, Oldenburgia arbuscula
RSA Tree No. 737.
Common names: Rabbit’s ears, Lamb’s ears, Donkey’s ears, Oldebburgia, Suurberg Daisycushion, Suurburg Kussinbos.
Family: Asteraceae, Compositae. (Daisy family: includes sunflowers, lettuce, chicory, marigolds). There are in excess of 1 900 genera and close to 33 000 species. This is possibly the second biggest plant family. In southern Africa, there are 246 genera and about 2 300 species. Local genera containing trees include Brachylaena, Oldenburgia and Tarchonanthus. Some members have flowers grouped in heads and the whole head may appear to be a single flower – like the “sunflower”. Surrounding each flower are bracts. Individual Flowers have sepals replaced by a pappus which may be bristle, plume, scale or awn like. Individual flowers are called Florets, which may have 5 fused petals. The Ovary is inferior and contains one Ovule and the Style has 2 lobes.
Name derivation: Oldenburgia– named after Franz Pehr Oldenburg who was a Swedish soldier who worked for the Danish Company of the East Indies. He also collected plants from 1772 – until he died from a fever in Madagascar in 1774. He spent a couple years in South Africa with Thunberg and Masson. grandis – large: presumably referring to the flowerheads.
Conservation Status: L C. (Least Concern)
This is a small Tree with a maximum height of 6m. It may also be a dwarf shrub. The Stem may reach a diameter of 46cm. Covering the stem are the remains of old leaf bases. The branches are stiff and spreading. The Bark is corky with woolly layers below. The young branches are stiff, spreading and appear white due to a woolly covering. Emma Mostert (associated with Rhodes University – department of Botany) describes the plant as, “A very strange plant that looks almost prehistoric”.
The large, distinctive, very stiff, oblong or ovate (egg-shaped) Leaves may be up to 35 x 15cm and occur at the ends of branches. These leaves are decussate (opposite pairs of leaves have successive pairs at right angles to each other i.e. rotated 90 degrees along the stem when viewed from above). Young leaves are white and hairy on both sides and initially grow in the form of a rose. From a distance the young white leaves against the darker older leaves have the appearance of a flower (photo 887). The simple leaves (have a single blade that may have incisions that are not deep enough to divide the leaf into leaflets) lack Petioles (leaf stalks). Individual leaves appear to be ear-shaped – hence the common names. The Apex is rounded or bluntly pointed. The Base tapers but expands near the junction with the stem. Margins are entire (with a continuous margin, not in any way indented) and widely curled inwards. The Blade of a mature leaf is bicoloured: the upper surface is a shiny dark green and the lower surface is a velvety creamy-white. The midrib and lateral Veins are clearly visible on both sides. They protrude below and are sunken above – where the midrib is distinctively creamy white.
Arising from the centre of the rosette of leaves is a solitary, stout, velvety stem, which terminates in the flattish Flowerhead that is up to 13cm wide. These honey-scented flowerheads are large, daisy-like Capitula (a dense inflorescence having a collection of usually sessile flowers in the form of a disc with the youngest at the centre). In the Involucre (one or more whorls of small leaves or bracts standing underneath a flower or flower-cluster), the outer layers of bracts is shorter. The flat Receptacle (is that expanded tip of the flower stalk from which the floral parts develop. It is greatly expanded in the Asteraceae and in Ficus) lacks bracts and has honeycomb-like cavities. The female Ray Florets (attractive, resembling petals of other flowering plants and occur in the outer circle of the capitulum) have a white corolla that is bilabiate (2-lipped). The outer lip is long or in 3 parts and the inner lip has 2 delicate, linear curled lobes. Here the anthers are sterile. In the many, regular Disc Florets the centrally placed flowers are bisexual. The base of the Anthers is arrow shaped. The Style, which emerges from an inferior Ovary, is circular in cross section and has very short branches. (Autumn but most of the year).
The Fruit is a Cypsela (Asteraceae fruit – a dry single-seeded fruit formed from a double ovary of which only one develops into a seed) with an apical tuft containing a single row of stiff bristles that act as a parachute to aid dispersal.
Distribution & Ecology
This plant is Endemic (Endemism is the ecological state of a species being unique to a defined geographic location) in the Eastern Cape – specifically from Makhanda (Grahamstown) to Port Elizabeth and occurs on hard Witteberg quartzite. Here most rainfall occurs during winter. This plant has fire-resistant bark and has the ability to resprout after a fire. Young leaves are hairy and these hairs protect them from the sun and wind.
The leaves may be poisonous. This is very interesting plant but difficult to cultivate. It needs to be planted in full sun in an open, well-drained acidic area.
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.
van Wyk, B. & van Wyk, P. 1997 Field guide to Trees of Southern Africa, Struik, Cape Town.