Indigofera L.
Tropical genus (of about 670 species, mostly African), closely related to Tephrosia, from which is differentiated by its bifurcate hairs. Both genera present compound leaves, small flowers, often reddish, and have a mainly central African distribution; sometimes towards the N they reach southern Morocco and the central Sahara (Algeria). In Mauritania and Egypt there are more than a dozen species, however many of these are herbaceous, only slightly lignified at the base. In this study we include clearly shrubby or larger plants only. It is a complex genus, with very similar taxa, in which some confusion still persists, evidenced by the large number of cross synonyms.
Key to species
1 Spiny shrub, with spinescent inflorescence 2
1 Plant not spiny 3
2 Inflorescence with 2-4 flowers; pod not lomentaceous, adpressed-hairy Indigofera spinosa
2 Inflorescence with (5)10-20 flowers; pod lomentaceous, silverydue to being covered by a dense indumentum of whitish hairs Indigofera spiniflora
3 Pod 0.5-1 cm, flattened, straight, with 2-4 seeds Indigofera arabica
3 Pod 1-4 cm, cylindrical, with 3-12 seeds 4
4 Plant with multicellular glandular hairs; stems and leaves silvery Indigofera argentea
4 Plant without multicellular glandular hairs; stems and leaves greenish or ashen 5
5 Leaves alternate Indigofera oblongifolia
5 Leaves opposite 6
6 All leaves trifoliolate; pod 2.5-4 × 0.15 cm, slightly or not at all lomentaceous Indigofera trita
6 At least some leaves with 5-9 leaflets; pod 0.7-1.2 × 0.3-0.4 cm,clearly lomentaceous 7
7 Leaves with 3-5 leaflets, silvery on both sides; pod strongly lomentaceous, with globular segments Indigofera articulata
7 Leaves with (5)7-9 leaflets, glabrous on the upper side; pod slightly lomentaceous, with cylindrical-ovoid segments Indigofera coerulea
Updated by: H. Sainz.