Westia dalbergioides (Baker) Taub.

Derris microphylla is a tree 5-20 m tall; crown feathery, branches ascending and umbrella-shaped; bark light grey to brown, slightly fissured; branchlets, petioles and buds golden-brown silky. Leaves imparipinnate, petiole and rachis 9-20 cm long; petiolule 1-2 mm long; leaflets 19-43, elliptical-oblong, 1.5-3.2 x 0.8-1.2 cm, rounded-emarginate at both ends, both surfaces thinly appressed brown hairy, glaucous below. Inflorescence an axillary raceme, 2-13 cm long, 1-3 together; flowers 7-8 mm long; pedicel 5-15 mm long; calyx campanulate; corolla dark-red to violet; standard 9 mm x 7 mm, bearing 2 glands at the base; stamens 10, monadelphous, 1 stamen free at the top and bottom adnate to stamen tube in center. Pod flat, elliptical to linear-lanceolate, 2.5-7 cm x 1.2-1.7 cm, 1-2(-5) seeded, indehiscent, narrowed at both ends, glabrous to puberulous, leaf-like along dorsal suture with a 1-2 mm wide wing. Seed 6 mm x 3 mm, brown-green. Derris is derived from Greek, meaning leather covering or skin, specific epithet means small-leaved.

Vetch tree flowers from August-January in Java.

The tree is tolerant of soils too poor for other species.

Locally common in secondary forest especially old ladangs in Upper Dipterocarp frorest.

D. microphylla occurs naturally in Sumatra, Peninsular Malaysia, Thailand, Myanmar and possibly Indo-China. Its natural occurrence in Java, where it is often planted is uncertain.

Propagation is by seed or cuttings.

Spacing recommended when planting for firewood and timber is 3 m x 3 m, with gradual thinning out to a final spacing after 10 years of 10 m x 10 m. Vetch is slow growing and requires little maintenance. It tolerates pruning and pollarding.

D. microphylla is attacked by the fungi Ganoderma pseudoferreum, Rosellinia and Ustulina zonata which affect its root system, and by several bagworm species.

Erosion control: D. microphylla has a superficial root system that protects soils against erosion. Shade or shelter: It is occasionally grown as a shade tree in cocoa, coffee and tea plantations especially on poor soils in Java. Reclamation: The tree establishes well on poor soils and may be used for reclamation. Soil improver: Vetch tree is used as green manure. Ornamental: Its abundant purple flowers make it a distinctive ornamental tree.

Fuel: The tree is a source of firewood. Timber: Wood is used as building material. Medicine: A poultice of roots or bark is used to treat itch in Malaysia.