Derris trifoliata Lour.

Loureiro, J. de (1790) Flora Cochinchinensis 2: 433. Type: Habitat in sylvis provinciae Cantoniensis Sinarum.

Derris, Threeleaf; Threeleaf Derris; Derris

Vine stem diameters to 4 cm recorded. Blaze odour resembles that of freshly cut green beans (Phaseolus vulgaris).

Leaves usually composed of 3-7 leaflets. Leaflets ovate to elliptic, about 5.5-15 x 2.5-8 cm. Leaflet stalks about 0.6-1.2 cm long. Stipules broadly triangular, about 1-2 mm long.

Inflorescence about 7-10 cm long. Flowers about 13 mm diam. Calyx tube about 3 mm long, calyx lobes scarcely developed and hardly discernible. Petals: standard about 11 x 11 mm; wings and keel about 10 mm long. Stamens 10, the filaments of nine stamens fused to form a tube open on one side. Staminal tube about 10 mm long, free part of the filaments about 3-3.5 mm long. One stamen free. Anthers about 0.5 mm long. Ovary + style about 12 mm long.

Fruits flat, about 3.5-5 x 2.2-2.8 cm, usually containing only 1 seed. Fruit wing very narrow and poorly defined, about 1 mm wide. Seed reniform, about 25 x 18 mm, rather plump. Radicle about 2 mm long.

Usually 2 cataphylls produced before the first pair of true leaves, cataphylls about halfway between the root system and the first true leaves. First true leaves ovate-cordate, apex acuminate, base cordate. Leaves unifoliolate, the pulvinus transversely wrinkled. Midrib +/- flush with the upper surface. At the tenth leaf stage: leaf or leaflet blades elliptic to ovate, apex acuminate, base cordate to obtuse. Leaves simple to trifoliolate at the eighth leaf stage but trifoliolate only beyond the twelfth leaf stage. Lateral veins about 10-15 on each side of the midrib. Tertiary venation reticulate. Stipules ovate, about 1 mm long. terminal buds and nearby sections of the stem clothed in prostrate, pale brown hairs. Seed germination time 35 days.

Occurs in NT, CYP, NEQ and CEQ. Altitudinal range very small, normally found just above tide level. Grows in monsoon forest, vine thicket and beach forest. Also occurs in Malesia and the Pacific islands.

This species has been used as a fish poison and as an arrow poison.

Although this species is not a source of commercial derris dust, having only a weak insecticidal action, it has been used as an insecticide in South-East Asia. Cribb (1981).