The Kaoko petalidium is a fast-growing, branched shrub with smooth,
white bark which contrasts with its striking, red, curved flowers
and ornamental, mottled bracteoles. The flowers are borne on short
spikes for the greater part of the year.
This is an erect, fast-growing, moderately branched, slightly aromatic
shrub, reaching up to 2.5 m tall with a tendency to scramble. It
becomes woody with age and has striking, white, smooth bark. It
has fibrous roots. Branches are first square and green, becoming
rounded and up to 30 mm in diameter at the base; the younger branches
have glandular hairs. The light green, egg-shaped leaves (heart-shaped
at the base) are spreading and are arranged in opposite pairs. The
petioles are 10-24 mm. The leaf blade is 40-65 X 30-40 mm, the margin
is shallowly saw-toothed with a prominent midrib and parallel veins;
the surface is sparsely glandular-hairy, becoming hairless and shiny;
the tip is acute.
The flowers occur in short racemes up to 40 mm long, borne in
the leaf axils. Each raceme consists of 3-8 flowers. Bracts are
leaf-like and ovate-lanceolate, about 15 X 8 mm and deciduous. The
base of each flower is covered by a pair of firm, purplish, mottled,
protective bracteoles, 25 X 16 mm. The glandular-hairy (sticky)
bracteoles are egg-shaped, concave and enclose the young flower.
The bracteoles soon become dry and grey, but persist on the branches.
The flowers (corolla) consist of a 30 mm long, yellowish green,
curved tube, 5-lobed at the end and 25 mm in diameter; the lobes
are red, oblong and spreading, the stamens are fused to the throat,
but free for about 10 mm and the anthers are about 5 mm long, are
positioned at the mouth of the flower or protrude slightly. The
smooth seed capsules are about 12 mm long.
Distrubution and habitat
The Kaoko petalidium is restricted to northwestern Namibia and occurs
in dry savannah in the Kaokoveld and Owamboland. The plant featured
here was grown from cuttings collected near Kaoko-Oktavi, growing
on dolomite outcrops in Mopane veld in frost-free areas. It grows
both in full sun and in the light shade of trees. Rainfall is mainly
during summer and ranges from 200-500 mm per annum, some years with
very little rain at all. Temperatures are high and often exceed
30° C during summer months, with cool nights during winter.
Its conspicuous red tubular flowers are pollinated by sunbirds.
In the wild, flowering is mostly after rain. The seeds, protected
in their firm capsules, are explosively released only during rain,
scattering the seed in all directions. Associated plants in its
habitat include the baobab, Adansonia digitata, Tylosema esculentum,
Cyphostemma currorrii, Sesamothamnus benguellensis, Sterculia africana
and Pelargonium otaviense. The plants are heavily grazed
by herbivores in the wild but resprout rapidly. The soil is a sandy
loam and well drained.
The genus Petalidium is derived from the Greek petalon meaning
leaf or petal. Coccineum refers to the red flowers.
The genus Petalidium with about 30 species recorded for
South Africa and Namibia (35 in the genus) are commonly found in
the summer rainfall regions in the bushveld (savannah). The genus
is diverse, ranging from small, scrambling herbs to large, robust
shrubs. Acanthaceae is a large horticulturally important family,
consisting of about 250 genera and 2 500 species. It is very well
represented in South Africa (50 genera). Other noteworthy horticulturally
important genera of the Acanthaceae in South Africa include Anisotes,
Barleria, Blepharis, Crossandra, Duvernoia, Hypoestes, Mackaya,
Ruellia, Ruspolia, Ruttya and Thunbergia. Species range
from small herbaceous plants to trees up to 10 m tall.
A characteristic of Petalidium and related genera is the
hygroscopic fruit capsule which, when moist, releases two flat seeds
explosively, hence its Afrikaans name rooi-tongklapper. Children
have the habit of placing the capsule under their tongue, which
then explodes like a cracker (klapper).
Growing Petalidium coccineum
Petalidum coccineum is a sight to see with its showy, red,
curved flowers and contrasting white stems, and is a colourful introduction
to horticulture. It is best grown in dry, subtropical, frost-free
gardens. It is very drought tolerant and its aromatic, leathery
leaves resist insect predation. It is easily grown from semi-hardwood
cuttings during the warmer months of the year. It is a rapidly growing
pioneer plant and will flower the first season after planting. It
also thrives in containers on verandas, and in colder climates can
be kept as a house or greenhouse plant.
As a garden shrub, the old, short, flowering branches tend to
become untidy and should be pruned during the winter months. The
young branches are soft and pliable, but soon become woody. In the
Botanical Society Conservatory at Kirstenbosch, the plant is extensively
used as a climber on the netted pillars in the house. This has proved
a great success and plants flower throughout the year with a peak
- Obermeyer, A.A. 1936. The South African species of Petalidium.
Annals of the Transvaal Museum 18: 151-162.
Ernst van Jaarsveld