Scientific name

Dodonaea viscosa (L.) Jacq.

Synonyms

Dodonaea viscosa var. angustifolia (L.f.) Benth.: Dodonaea viscosa f. angustifolia (L.f.) ; Dodonaea viscosa subsp. angustifolia (L.f.) J.G.West; Dodonaea viscosa subsp. angustissima (DC.) J.G.West

Common names

Switch sorrel, mkaa pwani (Kiswahili), Mwema-muthua (Kikuyu), musambya (Rukinga)

Family

Sapindaceae

Origin

Dodonaea viscosa is native to Australia, India, and tropical and subtropical Africa

Naturalised distribution (global)

Dodonaea viscosa is naturalised throughout tropical, subtropical and warm temperate regions of Africa, the Americas, southern Europe, southern Asia and Australasia and many oceanic islands with warm climates.

Introduced, naturalised or invasive in East Africa

Dodonaea viscosa is invasive in parts of Kenya and naturalised in parts of Tanzania and Uganda (A.B.R. Witt pers. obs.). It is cultivated in areas of western, south-east, coastal and northern Kenya; In Uganda, it is found growing wild around the Bwindi (Impenetrable) Forest in Kabale District and other highland areas in south western and western Uganda, in areas around Masaka  (southern Uganda) and on and around Mt Elgon; In Tanzania it is found from sea level to 2800 m but is more common in dry mountain forests. In Uganda it is widely believed to be indigenous.

Habitat

Dodonaea viscosa does well in a wide range of climates and soils. In East Africa it occurs in a variety of habitats; from riverine forest, sandy beaches to rocky soils on hillsides and arid marginal areas, mostly in disturbed areas where it may grow in homogenous stands. In Uganda it is common in highland areas where it tends to grow on well drained habitats usually between 1500-2500m altitudes (D. L. N. Hafashimana pers. comm.).

Description

Dodonaea viscosa is a thin-stemmed, leafy shrub or tree, usually 2-8 m tall with a light crown. The bark is grey, grooved, peeling and branchlets are rusty red and resinous (sticky).

Leaves are simple, thin, narrow, 5-10 cm long, 5-8 mm wide with  untoothed margins; leaf tip is round or pointed; leaves secrete gummy exudate which gives the leaves a shiny appearance.

D. viscosa has separate male and female flowers (is hermaphroditic). Flowers inconspicuous, pale green; sepals greenish-yellow, petals absent; stamens brown. The fruit is a distinctive capsule, with papery wings; wings pale brown or coral pink.

Reproduction and dispersal

Seed production is prolific. Seeds are black, smooth and are dispersed by wind.

Economic and other uses

Dodonaea viscosa makes a good hedge and is used for firewood, ploughs, tool handles, medicine (leaves and roots), bee forage, ornamental, land reclamation, dune fixation and as a tooth brush.

Environmental and other impacts

The precise management measures adopted for any plant invasion will depend upon factors such as the terrain, the cost and availability of labour, the severity of the infestation and the presence of other invasive species. Some components of an integrated management approach are introduced below.

The best form of invasive species management is prevention. If prevention is no longer possible, it is best to treat the weed infestations when they are small to prevent them from establishing (early detection and rapid response). Controlling the weed before it seeds will reduce future problems. Control is generally best applied to the least infested areas before dense infestations are tackled. Consistent follow-up work is required for sustainable management.

Minimising soil disturbance in pasture lands will reduce Dodonaea viscosa's ability to colonise. Manual and mechanical control can keep D. viscosa under short term control but it needs regular follow-up as the plant readily re-establishes. Roots need to be removed or the plant will resprout. Burning helps to control regrowth and destroy emerging seedlings. Goat grazing has been used as a control method though care must be taken as overstocking may end up promoting less desirable species.

The editors could not find any information about biological control programmes for this species.

Legislation

Not listed as a noxious weed by the state or governments in Kenya, Tanzania and Uganda.

References

AgroForestryTree Database online data sheet. Dodonaea angustifolia. http://www.worldagroforestrycentre.org/sea/Products/AFDbases/AF/index.asp. Accessed March 2011.

Maundu P. and Tegnas T. (eds.) (2005). Useful trees and shrubs for Kenya. Technical handbook No. 35. Nairobi, Kenya.

Katende A. B., Bernie, A. and Tegnas B.1995 (eds). Useful trees and Shrubs for Uganda. Identification, Propagation and Management for agricultural and pastoral communities. Regional Soil Conservation Unit, Kampala, Uganda.

Mbuya, L. P. , Masanga H. P., Bernie, A. and Tegnas, B. (1994). (eds). Useful Trees and Shrubs for Tanzania. Identification, propagation and management for agricultural and pastoral communities. Regional Soil conservation Unit, Nairobi, Kenya.

Editors

Agnes Lusweti, National Museums of Kenya; Emily Wabuyele, National Museums of Kenya, Paul Ssegawa, Makerere University; John Mauremootoo, BioNET-INTERNATIONAL Secretariat - UK.

Acknowledgments

This fact sheet is adapted from The Environmental Weeds of Australia by Sheldon Navie and Steve Adkins, Centre for Biological Information Technology, University of Queensland. We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) - Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).

Contact

BioNET-EAFRINET Regional Coordinator: [email protected]