Plants annual herbs, 15-80(200) cm tall; stems glabrous, often purplish. Leaves petiolate; petiole to 2 cm long, connate at base; blade ovate to lanceolate, 2-10 cm long, 0.5-1.5 cm wide, glabrous, base attenuate, margins entire to spinulose-serrate, tip acute. Capitula aggregated into glomerules; glomerules forming sessile axillary synflorescences 1-2 cm across subtended by small leaves; capitula with 1-2 florets, the outer capitula often radiate, the inner discoid; involucre of 2 phyllaries 2-4 mm long, at maturity enfolding the achenes; ray florets creamy-yellow, ± 1.5 mm long, ray about 0.5-1 mm long, suborbicular, without a pappus; disk florets 2-2.5 mm long, without a pappus. Achenes 2-2.6 mm long, black, ellipsoid.
Flaveria trinervia is native to tropical America, but is now a pantropical weed. In Somaliland and Somalia, it grows in dry stream beds, on fallow land, and in fields at 300-1350 m in regions N1-N3 and C1 of the Flora of Somalia. It has been known from Erigavo since the 1970s and become a common weed in nearby towns and agricultural fields. (Information from Hassan Dalac). It has also established itself on the grounds of the University of Hargeisa, suggesting that it probably grows in disturbed areas in much of Somaliland.
H. Pickering & A.I. Awale (2018) Introduction to the plants of Central Somaliland
Branching annual her with reddish stems, up to 60 cm. Leaves opposite, land-shaped, with marked veins and serrated margins. Flowers yellow in dense clusters, both terminal and in the leaf axils.
Habitat: Disturbed and wast ground; elevation 300-1350 m.
Note: GBIF records include introduced and cultivated plants. Consequently, the distribution shown often differs from statements about a taxon's native distribution.