Oldenburgia grandis 

(Thunb.) Baill.

Family: Asteraceae (daisy family)
Common names: Suurberg cushion bush, rabbit's ears, lamb's ears, donkey's ears (Eng.); bastersuikerbos (Afr.)

Oldeburgia  grandis

The appearance of this small tree or large shrub is unique. Its handsome, large, bicoloured leaves and strange flowers make this a distinctive landscape plant, a good choice for gardeners seeking something different.

Description
This is a slow-growing plant, reaching a height of up to 6 m with a stem of 460 mm in circumference . The bark is corky with a woolly layer below. Oldenburgia grandis has stiff, spreading branches with a woolly covering on the younger parts. The crown is composed of large, stiff, leathery leaves, bicoloured and stalkless, in rosettes at the ends of the branches. The leaves are up to 360 mm long and 150 mm broad, oblong or egg-shaped. The leaf margins are untoothed and rolled inwards, the surface somewhat rounded above. When O. grandis is mature it has deep green, shiny leaves with a greyish-white midrib. The undersides are velvety-white, sometimes with dark mould spots, with a broad and protruding midrib. The two surfaces make a lovely colour contrast. The young leaves are short, fat, white and densely furry. The leaves are said to be poisonous.

The flowerheads are borne on a long, stout, velvety-white stem, which springs from the centre of the rosette of leaves. Each flowerhead resembles a short, wide, purple brush covered thickly with velvety-white hairs. They are a bit like a giant thistle. The head opens wider as it matures, reaching 100-130 mm in diameter, to expose the fruits. The fruits are nutlets; thin, brown, crowned with a tuft of long, pale hairs. Flowering is irregular throughout the year, often with a burst in autumn.

Flowerheads


Old flowers / Seedheads

Old seedheads with young leaves in background.

 

Distribution and Habitat

Oldenburgia grandis occurs on the Suurberg inland from Port Elizabeth in Eastern Cape, to Grahamstown. The species is endemic to this area. It grows on the rocky outcrops of the Witteberg quartzite. Near Grahamstown it grows on hard sandstone outcrops.


Name derivation and historical facts
The genus Oldenburgia was named after P.F Oldenburg, a companion of the botanists, Thunberg and Masson on their travels to South Africa. Oldenburg died of fever in Madagascar in 1774.
The young leaves are remarkably like the ears of a young rabbit, lamb, or donkey in texture, hence the common names. The common name suikerbos refers to the flowerheads that bear some resemblance to those of the true suikerbos in the family Proteaceae. In reality there is little resemblance between Asteraceae and Proteaceae. The genus Oldenburgia has four species that are endemic to areas in Western and Eastern Cape. The other three species are O. intermedia, O. papionum, and O. paradoxa.


Ecology
This tree does not have a specific pollinator. It is visited by bees and butterflies. The dense silvery hairs on the young leaves serve to protect them from sun and wind damage.

Growing Oldenburgia grandis

Growing at KirstenboschIn warm, dry and essentially frost-free areas, Oldenburgia grandis makes a striking specimen. It is suitable for large rockeries and for other hot, dry positions in the garden, although it performs better on good soil with irrigation . This is a very handsome, decorative tree which can be planted in a small garden or courtyard. In temperate zones it requires the protection of a cool glass house.

Oldenburgia grandis needs to be grown in full sun with good ventilation in well-composted, sandy loam. This species needs to be watered moderately when in growth and kept dry in winter. In winter, the temperature needs to be maintained at a minimum of 7-10 º C.

O. grandis is propagated from seed and semi-hard cuttings in sand. Seed is difficult to germinate. This little decorative tree grows here at Kirstenbosch and is not commonly available in nurseries.


References

  • Palmer, E.& Pitman, N. 1972. Trees of southern Africa, vol. 3. Balkema, Cape Town.
  • Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of southern Africa, edn 3. Struik, Cape Town.
  • Leistner, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera. Strelitzia10. National Botanical Institute, Pretoria.
  • Goldblatt, P. & Manning, J. 2000. Cape plants. A conspectus of the Cape flora of South Africa. Strelitzia 9. National Botanical Institute, Cape Town.

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    Author
    Giles Mbambezeli
    Kirstenbosch National Botanical Garden
    February 2004

     


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