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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.
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Flowerheads
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Old flowers / Seedheads
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Old seedheads with young leaves in background.
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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
 In
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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