The genus Indigofera is composed of 'indigo' referring to the colour, and 'fero' meaning 'to bear'. The species name lyalli is of unclear origin, possibly named after Robert Lyall (1790-1831), a Scottish botanist and collector in Madagascar where the type specimen was collected. Another possibility is that it was named after David Lyall (1817-1895), another plant collector in Madagascar.

Indigofera is a large genus of over 800 species common to tropical and subtropical regions, mostly herbs and under-shrubs, with two tree-like species. More than 200 species are widespread in southern Africa,

This genus is classified under the legume or pea family, Fabaceae. Members of the pea family are fairly diverse and include economically important crops such as beans, peas and clover, as well as herbs, shrubs and a few beautiful flowering trees. The characteristic sweet-pea flowers of this family have a large upper petal (the standard), two side petals (wings) and two lower petals that are fused to form a 'keel' enfolding the stamens and pistil.

Other noteworthy members of this genus are:

• Indigofera jucunda, (often mistakenly called I.frutescens) a shrub or small, graceful tree (4-7 m). It also has grey bark and leaves that are dark green and compound with leaflets, but in this plant they are arranged in pairs of 4-7 with a terminal one. Flowers are small, pinkish white and sweetly scented. They are borne from December through to April in clusters on lovely, dainty spikes. Similar smooth, reddish brown, cylindrical pods appear from May to July.
• Indigofera natalensis, a shrub or slender tree up to 1-3m with pale grey bark. The leaves are shiny, dark green and compound - they are composed of one to two pairs of leaflets and a terminal leaflet with a drip tip . The flowers are small, white occasionally tinged with mauve, and borne on short delicate sprays from December to March. The fruits appear from May to June and are cylindrical red-brown pods.