Important Plant Families in South Africa - Mimosaceae

In order to facilitate the identification of our wealth of lovely South African trees, it is helpful to be familiar with the most prominent plant families in an area, as well as the characteristics that distinguish each plant family. Every month we will feature one of the most important and well represented plant families, focusing on easily recognisable features to assist identification.

Mimosaceae (Thorn tree family)

This very well represented plant family comprises about 100 tree species in southern Africa. Mimosaceae is one of three families belonging to the single Leguminosae family, the other two being Caesalpiniaceae and Fabaceae. These can easily be recognised by the fruit which consists of a seed bearing pod.

The most familiar representatives of this family are the Acacias and Albizias that are widespread throughout the bushveld regions of the country.

The family is distinguished by bipinnate leaves, sometimes feathery, and many have leaflets that fold up at night. Stipular scars are always present which, in the case of Acacias, are modified into thorns or spines. A distinctive feature is the thickening at each petiole and petiolule base while the fluffy, yellow or white flowers appear in the form of heads or spikes.

This family play an important part in nitrogen enrichment of soils as most members contain nitrogen fixing bacteria in the root nodules.

Various Acacias are of significant economic importance such as Acacia senegal, which produces gum arabic, an important component in the manufacture of various pharmaceuticals, cosmetics, foods, paints and adhesives. Products from Acacias are used in the tanning industry while the wood is also used for various commercial applications.

Members of the Mimosaceae family include; Albizia adianthifolia (Flat crown), Albizia tanganyicensis (Paperbark albizia), Acacia erioloba (Camel thorn), Acacia tortilis (Umbrella thorn), Acacia albida (Ana tree).