Mundulea sericea (Willd.) A. Chev.
Common names: cork bush, silver bush, Rhodesian silver-leaf (Eng.); kurkbos, blou-ertjieboom, olifantshout, visboontjie, visgif, mangaanbos (Afr.); omukeka (Herero); !gaeb (Nama/Damara); mosetla-thlou (Northern Sotho); omumbaganyana (Oshiwambo); umSindandlovana (Swazi); ntsandzandlopfu, maibana, mohato, mosikatse, mosita-thlou, moswaatlou (Tswana); mukunda-ndou (Venda); umHlalantethe, umSindandlovu (Zulu)
SA Tree No: 226
In a landscape characterised by grass and rock, all-year frost and drenching thunderstorms, Mundulea sericea stands out as the true star of the veld. In spring this silvery bush is covered in masses of purple flowers, attracting birds and insects. The leaves are soft and delicate, the flowers large, beautiful and pea-like. Throughout autumn, and often long into the winter months, silky silvery pods clad the many long and slender (virgate) branches of the tree.
Mundulea sericea is an attractive virgately-branched shrub or small graceful tree 0.5 - 7.5 (-12) m high, usually single-stemmed with a bushy, much-branched crown.
The bark protects the vascular tissue from frequent veld fires and frost. It is pale, corky and deeply furrowed — a fine contrast to the delicate silver-grey to light green foliage. M. sericea plants growing in an evergreen habitat devoid of fire are usually tall, single-stemmed trees with a greenish-yellow smooth bark with almost imperceptible longitudinal fissures. They are strikingly different from the more frequently encountered form from whence the English common name, cork bush, is derived. Young branches are tough and pliant. Leaves are alternate, imparipinnate (having an uneven number of leaflets, thus having a single, terminal leaflet), covered with silky silver hairs, 80-100 mm long in 4-10 pairs of leaflets with an additional terminal leaflet (all ± 13 mm long), oval to lance-shaped, pale green.
The flowers are showy and pea-like, carried in terminal clusters in a rich violet, mauve and lilac or even white. Flowers appear simultaneously with the new leaves in spring and early summer (October to February). The fruit are pods, ± 100 mm long and narrow, with thickened yellow-brown rims becoming brown-grey as they mature, velvety hairy; may persist on the branches throughout winter. Fruits mature from November to April. Each pod contains 1-11 brownish-green kidney-shaped seeds.
The wood is light yellow, tough, and hard and produces a strong, unpleasant scent when worked.
Currently this species is not threatened.
Distribution and habitat
The genus Mundulea consists of ±15 species, widespread throughout Africa, Madagascar, Mauritius, India, Sri Lanka and Papua New Guinea. Only a single species, M. sericea, is found in southern Africa. This species occurs in South Africa, in the west of Botswana, in Namibia and Angola, and northwards to tropical Africa, eastwards to Madagascar, India, Sri Lanka and Papua New Guinea.
These plants prefer well-drained, deep sandy or gravelly soil. They are found in grassland, savanna, wooded grassland and thicket, often on rocky ridges, wooded hillsides, flats and sometimes near rivers.
Derivation of name and historical aspects
The genus name is derived from the Latin word Mundulea = neat/elegant, the specific name from the Latin sericea = silver/silky, with reference to the compact, neat plant with its silver leaves when starting to sprout in springtime. Several of its African names mean 'that which resist elephants', with reference to the strong, tough branches.
The flowers attract birds and insects:
- the Marico, short-billed and greater double-collared sunbirds visit the flowers for nectar;
- the Natal Barred Blue, Common Blue, Dusky Blue and Common Pea Blue butterflies use the cork bush for either feeding or breeding or both;
- carpenter and other bees are responsible for pollination.
The leaves are browsed by both wild animals (elephants, giraffes, eland and impala) and domesticated animals (cattle and goats). The fruit is poorly dehiscent and the seeds are scattered around the mother plant by browsing mammals and birds.
The multitude of common names for Mundulea sericea alludes to its many uses and the degree of appreciation it has received in the past.
It can be used as accent plant in a rock garden, or a few clumped together make an attractive composition. It is an excellent choice for a container or grown as a bonsai. Plants grown together and pruned make an interesting indigenous hedge. The root-system is not aggressive.
The pounded bark, leaves and sometimes seeds and roots are used to poison fish. Unlike many other plants used for this purpose, the fish are usually killed and not just stunned by the poison. Leaves are stripped and pounded, placed in bags and thrown into the water. The dead fish are then collected for food at considerable risk, since there are cases where people have become ill after eating the poisoned fish. It is reported from east Africa that the poison is strong enough to kill small crocodiles. It is also said that strips of the bark were once tied round the legs of cattle whenever they were taken to the river to water in order to protect them from crocodiles. Surprisingly, the bark and leaves are eaten by cattle, goats, elephants and antelope without any ill effect.
Rotenoids from the bark have been used commercially as an insecticide. This group of chemical compounds in the bark, leaves and seed is responsible for the fish poison. It is reported that the strength varies geographically. Rotenoids such as rotenone, deguelin and tephrosin, isolated from M. sericea, have been used as arrow poison and for committing suicide. The bark is also said to be employed for homicidal purposes in parts of Africa.
To collect bark, stems are cut at ground level and the bark is stripped off as far as the branchlets. During the wet months the bark comes away quite easily and can be stripped off with the fingers. In winter, however, when the tree is not in an active growth stage, it has to be shaved off using a knife. The cutting of the stems at ground level does not kill the plant as it coppices freely (forms new branches from live plant parts).
In Kaokoland (northern Namibia) small branches are used as toothbrush sticks. The pounded leaves are mixed with lard and used as a hair dye.
Mundulea sericea is used in traditional medicine. The leaves are used by Zulus as an emetic to treat poisoning in both people and dogs. Infusions of the root are used to treat infertility. The powdered root is used in Venda in rituals to treat a married couple when the wife has had several miscarriages. During this ritual the couple are tied together with their backs against the tree.
Growing Mundulea sericea
Mundulea sericea is an attractive tree well worth introducing to a garden or used in various other horticultural ways to attract insects and birds, easily grown in well-drained soil enriched with some compost. Due to its size it is ideally suited for small gardens.
Put boiling water in a container, add fresh seeds and soak for a day. Seeds that do not show signs of swelling may be rubbed on medium-grained sand paper just enough to scratch the surface, and then re-soaked. Sow in spring or summer in a well-drained seedling mixture (sand, compost and sifted soil in equal parts). Cover the seed with a 4-6 mm layer of seedling-mix and place the trays in a warm, semi-shaded position. Drench the trays with a fungicide to prevent fungal infections. Water regularly; the seeds should germinate in 2-6 weeks.
When the seedlings reach the two-leaf stage (12-16 weeks after sowing), transplant them into nursery bags, pots or individual containers. Use sandy soil (or clay soil with 50% sand mixed in) with some well-rotted compost, and bone meal, taking care not to damage the long taproot. Seedlings and young trees usually transplant well.
The tree is relatively slow-growing with a growth rate of 50-100 cm per year and can initially be used as a decorative shrub in a container. The growth rate increases as the tree ages. Feed with a seaweed fertiliser.
Depending on the climate, the cork bush may either be deciduous or evergreen. It is hardy, drought-resistant, and requires moderate water and full sun. It may be more frost-sensitive in the Highveld where it should be planted against a north-facing wall or in a warmer spot in the garden.
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S.P. Bester & A. Grobler
National Herbarium Pretoria
Plant Type: Shrub, Tree
SA Distribution: Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga, North West
Soil type: Sandy
Flowering season: Spring, Early Summer
Flower colour: Purple, Mauve/Lilac
Aspect: Full Sun
Gardening skill: Average