Important Plant Families in South Africa - Fabaceae

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.

Fabaceae (Pea family)

This family is widespread and well represented in southern Africa where in the region of 80 tree species occur, and is one of the three families characterised by a legume or pod as fruit type, the other two being Caesalpiniaceae and Mimosaceae.

Members of this family are easily recognised by the distinctive butterfly-like flowers that have unequal petals, with the uppermost petal the largest, two stalked side petals that form ‘wings’ and the basal petals joined to form a boat-like structure or keel.

The leaves are mostly imparipinnate or tri-foliolate or occasionally simple with stipules always present. A useful vegetative feature that aids identification is the conspicuous thickening at each petiole and petiolule base.

Many members of this species have root nodules containing nitrogen fixing bacteria, making them invaluable for enriching the nitrogen content of soils.

This species is extremely varied and has numerous members that offer great economic value. Some of these include herbaceous species such as the garden pea (Pisum sativum), the peanut (Arachis hypogea) and various beans such as (Phaseolus). Forage plants such as lucerne (Medicago sativa) also belong to this important family. Amongst the garden ornamentals the coral tree (Erythrina) and Wisteria are widely grown.

Some members of this family include Baphia massaiensis (Sand camwood), Podalyria calyptrata (Water blossom pea), Erythrina caffra (Coast coral tree), Bolusanthus speciosus (Tree wisteria), Calpurnea aurea (Wild laburnum), Virgilia oroboides (Blossom tree) and Indigofera jucunda (River indigo).