© G Nichols

Ehretia rigida is a deciduous small tree or shrub, usually multistemmed, with an untidy rounded crown. It has tangled branches which arch downwards or droop. This rather haphazard look gives it its common names, puzzle bush and deurmekaarbos.

Description
Ehretia rigida can grow up to 9 m in height. The bark is very smooth and grey on new branches and rough on older branches and stems. The plant has an alternate leaf arrangement but the leaves seem to grow together in clusters at the tips of its short branches. The leaves can be smooth or covered with stiff hairs that are rough to the touch. It has small leaf stalks of about 2 mm long. The flowers grow in dense clusters on the branches. These pale mauve, blue or white flowers can only be seen in spring with male and female flowers on different plants. They have a diameter of 7 mm and are sweetly scented. The fruits are round, orange to red, turning black when ripe and are eaten by wild animals. Parasitic plants, such as the mistletoe, Viscum rotundifolium, are often found on the puzzle bush.

© G Nichols

Distribution
The plant occurs in a wide variety of habitats, including wooded grassland, karroid vegetation and bushveld. In South Africa it occurs throughout the eastern half of the country and also in Botswana, Swaziland and Lesotho.

Derivation of name
Ehretia was named after an 18th century botanical artist, R.D.Ehret. The Latin word rigida means stiff, referring to the hard leaves.

Other species of the genus in southern Africa are Ehretia amoena, E. obtusifolia, E. alba, E. coerula, E. cymosa and E. namibiensis. Three of these, E. rigida, E. amoena and E. obtusifolia occur in South Africa. Ehretia rigida is further divided into three subspecies, namely, E. rigida subsp. rigida, E. rigida subsp. silvatica and E. rigida subsp. nervifolia, which occurs naturally in the Witwatersrand National Botanical Garden.

Ecology
The tree is a food source to domestic stock and wild animals, such as the kudu, nyala, bushbuck, impala and grey duiker. Its fruits are eaten by people and many birds such as the Crested Francolin, Helmeted and Crested Guineafowl, Southern Yellowbilled Hornbill, Crested Barbet, bulbuls and starlings.

Uses and cultural aspects
Ehretia rigida is very attractive to birds and insects and is therefore a wonderful addition to the wildlife garden. It can be pruned to make a shape and can also be used as a hedge in a garden. Ripe fruits of this plant are edible but not tasty. For traditional, medicinal purposes, the roots are powdered and used to treat small cuts in the skin. It is used over the abdomen and chest to relieve pains and is also used to treat gall sickness in cattle. The plant is believed to bring luck to hunters and is also used to protect huts and crops from hail. Hunters use branches of this plant to make hunting bows and fishing baskets because they are strong and flexible.

Growing Ehretia rigida

The puzzle bush is becoming very popular as a garden plant because it is hardy and drought resistant. It can easily grow from seed and cuttings. Use river sand or a mixture of river sand and compost to sow the seedlings. They should be sown in a seedling tray and be covered with a thin layer of sand. Do not sow the seeds too deeply. If they are sown properly, the seeds will take 10-20 days to germinate. Plants should be kept in nursery bags until the next season before they are planted into the ground. The plant has a fast growth rate of about 600-700 mm per year.

References

• CARRUTHERS, V. 1997. The wildlife of South Africa. Struik, Cape Town.
• COATES PALGRAVE, M. 2002. Keith Coates Palgrave Trees of southern Africa, edn 3. Struik, Cape Town.
• VAN WYK, A.E. (Braam), VAN WYK, P. & VAN WYK, B-E. 2000. Photographic guide to trees of southern Africa. Briza Publications, Pretoria.
• VENTER, F., & VENTER, J-A. 1997. Making the most of indigenous trees. Briza Publications, Pretoria.

Phillemon Ndou
Witwatersrand National Botanical Gardens
December 2003