Willem says: 'The Phyto-Philes are for plant lovers of every size and shape, colour and flavour. As with my Colours of Wildlife column, I'll be featuring one species per article, illustrated with sketches, paintings, and/or photos. Over time I hope to be showcasing the amazing diversity of weird and wonderful plants that occur in South Africa, while also from time to time looking at the flora of other countries. While featuring many spectacular species, I'll not be neglecting the smaller, more humble kinds that are nevertheless fascinating in their own right.'

Here you have yet another of Africa's iconic trees! This is a Leadwood, Combretum imberbe. It belongs to the Bushwillow genus, and like its relatives it bears characteristic four-winged, dry fruit. The species occurs in the warm northern parts of South Africa, and from there northwards as far as Tanzania. It can be distinguished from the others by its size (being one of the largest Combretums in South Africa), by its craggy look, and by its bark, the grey surface of which is divided into lots of small, rectangular blocks, like crocodile skin. They have small leaves with a slightly yellowish tint, and their crowns tend to be rather open and diffuse in shape. They are deciduous. The photo here was taken in the Musina Nature Reserve, famed for its Baobabs but also hosting lots of other interesting trees. This is a particularly large individual, about 20 m/67' in height, towering over the Mopane and Corkwood trees around it. Leadwoods can achieve a trunk circumference of 4.4 m/14.5'.

But strangely enough, a Leadwood is even more distinctive when dead! Its wood, which as you may gather is extremely heavy, is also extremely hard. A tree that dies, simply remains standing! Its leaves drop, and its bark flakes away, but the 'skeleton', now with a smooth, plain, light grey to white surface, can remain standing for years. Indeed, they are distinctive elements in the Bushveld. Even the dead tree has value! Many birds seem to prefer perching in these white tree-skeletons, maybe because they have a clear view down and around due to the lack of leaves. Although no woodpecker can tunnel into the wood, the trees often have natural knot holes, cavities and hollow branches that can be used by them and other hole-nesting birds, or squirrels and other critters. My drawing shows a typical deceased specimen.

The one thing that can destroy living or dead leadwood trees is fire. Old trees are especially vulnerable, since their main trunks, and sometimes some of the branches as well, become hollow and this causes a chimney effect in a burning tree, funneling in oxygen. A tree that starts burning burns away completely; the coals left over from burnt trees have been recorded still smouldering several weeks after a bush fire. In the end all that remains is a pit of ashes, the fire even proceeding down to consume the subterranean roots.

But leadwoods growing in fire-free areas can live very long, up to a thousand years in some cases. The living trees also have ecological value. Elephants, giraffes and several species of antelope browse their leaves. The trees, when large, provide nesting sites for many other birds. The natural presence of leadwood trees indicate 'sweet veld', meaning the soil is rich in nutrients and the grasses mainly very palatable. Leadwood bark exudes an edible gum, used by the San/Bushmen of the Kalahari, and also consumed by Bushbabies.

The leadwood's wood is also very sought after. It is so heavy that it sinks in water – it has an air-dry weight of 1200 kg per cubic metre/about 1900 lbs per cubic yard. This wood is very hard to work, rapidly blunting tools, but since the trees are naturally rather straight-growing, trunks and branches can be used for poles, posts, columns and props with little or no finishing. They are extremely strong and last practically forever; termites and wood borers can't do a thing against them. Tenacious woodworkers can shape this very hard wood with lathes; it is fine-grained and can be used for sculptures, ornaments and furniture. Traditionally the wood is patiently sculpted into mortars in which grain is pounded into meal. Before the widespread availability of iron and steel, leadwood was used for making the blades of hoes and ploughs. Particularly straight specimens have mostly been cut down for making railway sleepers. Leadwood branches, trunks and roots are often used as aesthetic elements in gardens, giving a somewhat 'natural' look and striking visual features in the garden around which other plants can be grouped. The wood is especially sought after as firewood, being so long-burning and giving off an intense heat. And the very fine, white ash that's left over can be used as a substitute for lime to whitewash buildings, or even as toothpaste! An extract from the bark covering the roots is used for tanning leather, and different parts of the tree have a variety of traditional medicinal uses. The Herero people of Namibia revere these trees as ancestors, and protect them from harm.

I've not yet grown leadwoods; the species is not very suited to urban gardens, being rather slow-growing but eventually reaching a great size. It is very well suited to game reserves and farms, and should be planted in rest camps. While small they can still be conversation pieces and help folks with learning to identify them, with the leaves and pods within easy view. Another good place to plant them is on the banks of rivers, lakes and ponds.

To grow them, collect pods … many will be parasitized by beetle grubs and other insects. Open the pods and inspect the seeds, discarding those that are damaged. The healthy seeds should be sown in a well-draining soil mix, with plenty of sand and just a bit of compost. Place the seeds on the surface and strew a thin layer of sand over them. Seeds germinate best in fairly hot and moist conditions. Germination might under the best conditions still be poor and erratic, so some patience and fortitude is needed. Transplant the seedlings into individual bags when they form their first two true leaves; they can grow there for a year or two but should be transplanted into their final growing spots when they reach a height of 20-25 cm/8"-10". They should be kept moist but not too wet; once a metre/yard in height they can survive an average dry winter. They can only tolerate light frost, though. They typically grow fairly slowly but under ideal conditions can gain about half a metre/yard in height per year.

Colours of Wildlife Archive

Willem

23.12.13 Front Page

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