Meet the Trees in Namibian road reserves

Lay-bys offer an excellent opportunity to get to know indigenous trees in Namibia. Here they are not obscured by other trees, their shape is clearly visible and one can stop to look closely at them. In general, scattered trees inside the road reserve are beautiful to see. They break the monotony of our roads which often seem to stretch out straight into infinity. Even if one does not have the time to stop, the pool of shade they cast is a relief to see on a hot day. Attracting birds and insects, trees provide variety and entertainment for road users.

This lovely Silver Cluster-leaf (Terminalia sericea) can be found about 40 km south of Otjiwarongo to the west of the B1. Its most obvious distinctive features are the numerous, flat, pink to rose-red two-winged fruit, which develop from March onwards and remain on the tree for a long time, making identification easy. During spring and summer the Silver Cluster-leaf stands out against the other vegetation because of its beautiful silvery green foliage. It is often the dominant species on sandy soils, especially in the eastern and north-eastern parts of the country.

In Namibia this tree is known by several diffe-rent names: German "Gelbholzbaum" and Afrikaans "Geelhout" both refer to the yellow
colour of its wood, while the other Afrikaans name "Vaalboom" probably has to do with the pale green colour of its young foliage. H. Omuseasetu; Nd. Omugolo Ky. Omwoolo N/D. /gab. The botanical genus name Terminalia is derived from the arrangement of its leaves, which are clustered at the end or 'terminus' of the twigs, hence also the name 'Cluster-leaf'; sericea means 'like silk' and refers to the fine silky hair covering the leaves.
The Silver Cluster-leaf always grows on deep sandy soil where it may be very abundant. A few beautiful specimens occur along the B1 in the vicinity of the tree on the photo. Furthermore, it is very common on the deep sandy soil of the north-eastern Namibia and may be found as far a field as Koes in the south to Epupa in the northwest. It even occurs on patches of windblown sand in the valleys of the Karstveld.
The Silver Cluster-leaf is a beautifully structured tree with a straight dark trunk and a characteristically layered crown. Although the tree may reach a height of up to 12 m, in the Omaheke region it often forms extensive stands of shrubby growth, only 1 - 2 m high.
The trunk is grey to dark brown, deeply fissured lengthways, and rough. The red-brown to purplish bark on young twigs peels to reveal the light brown underbark.
Pale green to blue green and covered in silky hair, the leaves give a silvery appearance to the entire tree. They are simple and entire and when rain is plentiful the leaves tend to be lar-ger and less hairy than in dry years.
The inconspicuous creamy to yellowish flowers appear from October - November in slender drooping spikes and have a somewhat unpleasant smell.

Most of the numerous two winged pink fruit hang below the branches, while the leaves tend to grow quite erect along the upper side of the branches. When in fruit, this tree with its dark trunk and branches, its graceful shape and silver-green canopy flecked with the dark pink fruit is a lovely sight, softening the harshness of the savanna landscape. With age the fruit turn a brown colour.
The wood is yellow, fine grained, strong and elastic. It is also insect resistant and thus often used for fence posts, for building traditional housing and for tool handles. Attractive rustic armchairs and settees can be fashioned from this wood. It provides good firewood. Because of the straight growth-form young trees are often used as mokoro (canoe) poles. In the northern regions the inner bark serves to lash together the frames of traditional houses and is also used in the making of grain-storage baskets. Because of their elasticity young branches may be used for making snares. People along the Kavango pound the root bark into a sticky mixture to seal their dugout canoes. On the Waterberg Plateau the leaves are regarded as an important component of the diet of eland. The nutritional value for livestock can be greatly improved by supplying the animals with chemicals that neutralise the tannin content. Tannin reduces the absorption of proteins in the sto-mach of cattle and thus slows down the digestive process. Certain chemicals added to the mineral lick provided to cattle improve the digestibility of proteins and speed up the passage of the leaves through the intestines, thus enabling the animals to eat more and to ingest more nutrients. The bark also contains tannic acid which can be used for tanning. It imparts a yellowish colour to the leather. Even the galls mentioned below have a high tannin content.

When crushed and soaked the fresh leaves yield a blue dye. The bark of the Silver Cluster-leaf is also used for glazing pottery to which the addition of the hair on the leaves imparts a silvery sheen. Dried leaves are sometimes smoked instead of tobacco.
Extracts of bark, leaves and roots contain tannic acid and are used to treat diarrhoea, menstrual cramps, stomach disorders, pneumonia and eye infections. Strips of bark or the leaves can be chewed to treat bad colds or persistent coughing. Drinking a decoction of the roots or chewing the bark cures headaches and is considered an effective treatment for malaria. The dried roots pulverised and mixed with the dried inner parts of the conspicuously yellow and black blister beetle are used to treat Schistosomiasis (Bilharzia). A powder made of the dried roots speeds the healing of wounds, while the pulverised bark mixed with maize meal is used to treat diabetes. A glycoside has been isola-ted from parts of this tree and has been found to have an effect on heart and pulse rate. An edible yellow caterpillar with black stripes frequently feeds on the leaves of the Silver Cluster-leaf.

The edible gum of this tree is often used as glue for poison arrows. It is carried along on a stick in the quiver with the arrows and softened with a little saliva before use. Hunters sometimes rub the string of their bows with the leaves to make them smooth and strong.
Many household items used for stirring, twirling or pounding of food are made of this wood. Medicinal or lucky charms are often attached to fine necklaces made by twisting narrow strips of Silver Cluster-leaf bark around each other.
In some areas people are very reluctant to fell this tree before the crops have been harvested, as it is believed that cutting down a Silver Cluster-leaf may cause hailstorms. Twigs or sticks of this tree also feature during ceremonies in honour of the ancestral spirits, as they are said to facilitate contact with these spirits.

Galls (ball-shaped woody growths about 2 - 3 cm in diameter) are often found on the twigs of the Silver Cluster-leaf. They are caused by the larva of an insect injecting certain chemical substances into the twig, resulting in the abnormal growth. The fruit are also sometimes deformed into clusters of velvety worms as a result of the activities of a similar parasitic insect. Similar galls may often be found on various Combretum species, which belong to the same family as the Silver Cluster-leaf.Three other tree species frequently associated with the Silver Cluster-leaf in the north eastern parts of Namibia are the Kalahari apple-leaf or Kalahri Omupanda (Lonchocarpus nelsii, recently renamed as Philenoptera nelsii), the Variable Combretum (Combretum collinum) and the Red Seringa or Omutundungu (Burkea africana).
This lovely tree would be a wonderful garden specimen. However, the seeds do not germinate easily and seem to thrive only in their na-tural habitat. The tree can withstand some frost and is drought resistant, but grows slowly.

[For much of the information on this tree I am greatly indebted to two very informative and entertaining books, namely Roodt, Veronica: "Trees & Shrubs of the Okavango Delta", ISBN 99912 0 241 2, published by Shell Oil Botswana and Leffers, Arno: "Gemsbok Bean & Kalahari Truffle" ISBN 99916 0 491 X, Gamsberg Macmillan]