|
These beautiful trees with their distinctive butterfly-shaped leaves
and strange seeds are, for many, the essence of South Africa's lowveld
areas, along with interesting bird and insect life and game animals.
They are also an extremely important food source for animals and
people. Vast tracts of uninterrupted mopane scrub and woodland characterize
the hot, low-lying areas near the Limpopo River in the far north
of South Africa.
Description
 The
mopane can be a shrub or a tall tree up to 30 m in the northern
part of its range, depending on soil conditions and water availability.
It has a tall, narrow crown. The compound leaves are divided in
two so that the leaflets resemble butterfly wings or a camel's foot.
There is a tiny point at the join of the two leaflets which is the
remnant of a third, terminal leaflet. Crushed leaves have a turpentine
odour. It is a deciduous (sometimes semi-deciduous) tree with lovely
autumn and spring colours. Sprays of small, green flowers appear
in December and January.
 These
are followed by pods which ripen between April and June and are
flat and somewhat kidney-shaped. They change from green to light,
finely speckled brown. The flat seeds inside are sticky from resin
exuded by glands which cover them. The strange appearance of the
seeds is from the convolutions in their surface. Some might say
they resemble tiny, flat mottley-brown brains! The greyish brown
bark is very deeply fissured in vertical fissures. It has a rough,
ropy appearance and is very distinctive.
Distribution
The mopane grows in hot, dry, low-lying areas, 200-1 150 m, in the
far northern parts of South Africa, into Zimbabwe, Mozambique, Botswana,
Zambia, Namibia, Angola and Malawi. It is found growing in alkaline
(high lime content) soils which are shallow and not well drained.
It also grows in alluvial soils (soil deposited by rivers). In South
Africa and adjacent areas of Botswana and Zimbabwe, the trees tend
to vary between 4 and 18 m, often called mopane scrub but also sometimes
taller and forming woodland, where further north the trees are taller
and form tall woodlands referred to as cathedral mopane. I recall
visiting Botswana's Okavango Delta and encountering miles of lush
mopane woodlands of great height, interspersed with waterlily-filled
ponds, quite different to the familiar mopane scrub of the south.
This tree does not grow well outside of suitable hot, frost-free,
summer rainfall areas. It would be tolerant of poor, alkaline soils,
however.
Derivation of name and historical aspects
The name Colophospermum is Greek for oily seed, in reference
to the resinous seeds. The part of the name, colophos, apparently
refers to the strong turpentine smell of the resin. Colophony is
another name for rosin, a substance obtained from turpentine. The
species name, mopane is taken from the local name for the tree.
The genus Colophospermum only occurs in Africa and there
is only one species in the genus. The mopane is in the pea family
(Fabaceae) This huge and important family is further divided into
three subfamilies; the mopane lies within the Caesalpinioideae.
The other two subfamilies are the Mimosoideae, which contains amongst
other genera, the acacias; and the subfamily Papilionoideae into
which, plants such as the indigos (Indigofera) and rooibos
tea bush (Aspalathus) are placed. C. mopane can be
confused with the small false mopane, Guibourtia conjugata
in areas where they co-occur (in the far northeast corner of South
Africa), although the seeds of the false mopane are not convoluted
or resinous and the bark not as rough and fissured. The leaves also
do not have the tiny spike-like remnant of the third leaflet.
Ecology
If you were to travel through areas of mopane woodland in the heat
of the day and wished to stop and rest in the shade, you would have
trouble finding any! To save water, the leaflets fold together and
present the smallest surface area toward the sun, thereby reducing
exposure of the leaf surface. This also prevents much shade from
being cast. The mopane is often deciduous in winter, possibly another
adaptation to drought, since winters are not very cold in the lowveld,
but they are dry. The lovely reddish new leaves only emerge in October
in anticipation of the first rains. Game animals, particularly elephants,
enjoy the protein-rich leaves and pods. Elephant pressure may be
part of the reason for the stunted appearance of some areas of mopane
scrub. Domestic animals find the pungent leaves unpalatable at first
but will feed on them once used to the taste. The meat and milk
is apparently untainted with a turpentine flavour. The young leaves
have a higher protein content and are more palatable but even the
dry, fallen leaves yield valuable protein for stock and game.
Hole-nesting birds such as hornbills favour mopane woodlands as
they offer many nesting sites. 'Mopane manna' is picked off the
leaves by people and baboons. This is a sweet-tasting, waxy cover
on the juvenile stage of a sap-sucking insect (related to leaf-hoppers)
known as the mopane psyllid, Arytaina mopani. The well-known
mopane worm, which is the large caterpillar of the Imbrasia belina
emperor moth, the Gonometa moth and the caterpillar of the foxy
charaxes butterfly, Charaxes jasius saturnus, feed
on the mopane. The tiny mopane bee, Plebina denoita, which
many know from its (sometimes successful) attempts at crawling into
ones eyes, ears and nose, produces a small amount of edible honey.
They make their nests in hollow trunks with a small wax tube as
the opening to the outside. Mopane seed pods do not split open of
their own accord and the seeds can germinate while still in the
pod.
Uses and cultural aspects
In summer the leaves are fed on by swarms of fat, dark greyish mopane
worms, which can reach almost 10 cm long. These are rich in protein
and are eaten by people, either roasted or dried. The sale of dried
mopane worms is an important income source for many people, creating
a local economy.
Other traditional uses of the mopane tree include the making of
houses and kraal fences, twigs chewed as tooth brushes, the bark
is used to make twine and for tanning, and the leaves used for healing
wounds. The hard, reddish heartwood timber was used to make railway
sleepers and as props for mining activities. This is one South Africa's
heaviest timbers and is apparently difficult to work because of
its hardness but this also makes it termite resistant, therefore
a popular choice for fence posts and flooring. The Gonometa moth
caterpillar spins silken cocoons which are harvested as wild silk
to make cloth.
Growing Colophospermum mopane
The mopane has a rather limited horticultural potential in areas
outside of the hot, summer rainfall areas of South Africa. It is
not tolerant of cold and frost. It would be a good addition to a
wildlife garden and for adding autumn and spring interest. It is
best grown from seed. Seeds can be removed from ripe pods or sown
in the pod. Removing the seed from the pod does speed up germination
but needs to be done carefully. They should be sown in flat seedling
trays in river sand. Place the seeds on the sand surface. Keep the
trays moist so that the seed can absorb water to germinate. Once
the seed has germinated they will be susceptible to infection from
damping-off fungi, therefore reduce the amount of water. It also
helps to use clean, new river sand, sterilize it if possible. The
seedlings are initially slow growing but the growth rate speeds
up once a height of about 200 mm is reached. Transplanting will
need to be done with care, try to avoid damaging the roots. Use
loamy soil with some sand and compost added, in black nursery bags
and water well after the transplanting operation.
References
- ESTERHUYSE, N., VON BREITENBACH, J. & SÖHNGE, H. 2001.
Remarkable trees of South Africa. Briza Publications, Pretoria.
- GERMISHUIZEN, G. & MEYER, N.L. (eds). 2003. Plants of southern
Africa: an annotated checklist. Strelitzia 14. National
Botanical Institute, Pretoria.
- GRANT, R. & THOMAS, V. 2002. Sappi tree spotting:
Lowveld. Jacana Education, Johannesburg.
- HANKS, P. (ed.). 1979. Collins dictionary of the English
language. Collins, London, Glasgow.
- LEISTNER, O.A. (ed.) 2000. Seed plants of southern Africa: families
and genera. Strelitzia 10. National Botanical Institute,
Pretoria.
- COATES PALGRAVE, M. 2002. Keith Coates Palgrave Trees of
southern Africa, edn 3. Struik, Cape Town.
- PALMER, E. & PITMAN, N. 1972. Trees of southern Africa
2. Balkema, Cape Town.
- PICKER, M., GRIFFITHS, C. & WEAVING, A. 2002. Field guide
to insects of South Africa. Struik, Cape Town.
- SCHMIDT, E. et al. 2002. Trees and shrubs of Mpumalanga and
Kruger National Park. Jacana, Johannesburg.
- VENTER, F. & VENTER, J-A. 1996. Making the most of indigenous
trees. Briza Publications, Pretoria.
- VAN WYK, B. & VAN WYK, P. 1997. Field guide to trees
of southern Africa. Struik, Cape Town.
- VON BREITENBACH, J. et al. 2001. Pocket list of southern
African indigenous trees including selected shrubs and woody climbers,
1st abridged impression of 4th edn. Briza Publications & Dendrological
Foundation, Pretoria.
|
|
Alice Aubrey
Walter Sisulu National Botanical Garden
January 2004
|
|
