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An ideal water wise ground cover plant for dry gardens, Aptosimum
procumbens is one of the treasures of the arid and semi-arid
parts of South Africa.
Description
These perennial plants form 'carpets' of up to 1 m in diameter.
When in full bloom it is covered with dark blue or violet, trumpet-shaped
flowers that can appear at any time of the year but mostly during
spring to summer. Leaves are alternate, usually densely crowded
on long or short shoots, linear, lanceolate, elongated or spathulate
entire. The fruit is a thick-walled capsule opening at the top and
often persists after seeds are dispersed.
Distribution
A. procumbens, and other species of Aptosimum, have
a wide distribution range from parts of Namaqualand, Bushmanland,
the Great Escarpment, the Northern, Upper, Great and Little Karoo,
Northern Cape and Namibia. It often occurs in abundance on floodplains,
flats, ridges, crowns, disturbed ground and mountain plains.
Derivation of name and historical aspects
The name Aptosimum is Greek in derivation, a meaning
not and ptosimos meaning deciduous (which in turn comes from
ptosis meaning 'fall') and refers to the fruit, a capsule
which is retained on the plant even after the seeds have been released.
Ecology
The trumpet-shaped flowers are clearly designed for insect pollination
and the flower petals acts as ideal landing pads. Their shape and
colour lead to the assumption that bees are their pollinators. They
are 'gullet flowers' which means that the corolla is tubular over
the greater part of its length and very narrow in the basal region,
protecting the nectaries from all but long tongues or minute visitors.
Although bees visit flowers from time to time, it appears that the
primary pollinators are pollen wasps (Vespidae, Masarinae), particularly
from the genus Celonites. Even more peculiar is that Karoo
violets receive more frequent visits from specific species of Celonites
in specific distribution localities, C. clypeatus and C.
andreis for example, throughout the Karoo. These little wasps,
on average about 10 mm long, are blackish and have red or red and
white markings. They have long retractable tongues with which they
collect the nectar.
 Uses
and cultural aspects
It is quite surprising that Karoo violets with their striking beauty
have received very little horticultural research, as they really
show great potential as garden plants especially in the dry parts
of the country. With specific selection and mass cultivation there
should be no reason why they can't be used in flower boxes, hanging
baskets or ground covers and become just as popular as our pelargoniums,
senecios, etc. It is recorded that Aptosimum was cultivated
as an ornamental in England from seed sent there by Burchell and
Ecklon from as early as 1815 to in about 1828. The plants are said
to be of medicinal value and is are used to treat krimpsiekte in
sheep, an acute and serious sickness that affects the joints, muscles
and stomach, often resulting in starvation and ultimately death.
Growing Aptosimum procumbens
There is no doubt that Karoo violets would do well as garden plants.
They can be used as pot subjects, in hanging baskets, in flower
boxes and as ground covers. Plants prefer sunny positions and can
withstand prolonged periods of drought, making them ideal for a
water-wise garden. Another unusual application is planting Aptosimum
in between paving slabs in the same way that ornamental grasses
are used to soften surfaces.
Although very possible, some difficulty is experienced with propagating
plants from seeds. A better option is to propagate plants from cuttings.
Only the soft and young tips of shoots should be used and material
must be sought from healthy and vigorously growing plants. Cuttings
must be about 10 mm long and planted in a coarse, sandy medium which
must be kept moist and warm.
References
- CODD, L.E. 1983. Aptosimum procumbens. The Flowering Plants
of Africa 47: t. 1880.
- GESS, S. 2000. Karoo violets and pollen wasps. Veld &
Flora 86: 170, 171.
- LEISTNER, O.A. (ed.) 2000. Seed plants of southern Africa: families
and genera. Strelitzia 10. National Botanical Institute,
Pretoria.
- SHEARING, D. 1997. Karoo. South African Wild Flower Guide
6. Botanical Society of South Africa, Cape Town.
Werner Voigt
Karoo Desert National Botanical Garden
December 2003
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