Glycine max

Tap-root can extend 2 m deep in good soil conditions, with secondary roots exploring the upper 15-20 cm of the soil. Stem is brownish or greyish pubescent. Leaves are alternate, with3(-7) leaflets and 2–20 cm long petioles. Stipules are broadly ovate, 3-7 mm long. Leaflets are ovate to lanceolate, 3–15 cm × 2-6(-10) cm, base cuneate or rounded, apex acute to obtuse, entire, glabrous to pubescent. Inflorescence is an axillary false raceme up to 3.5 cm long, often compact, densely hairy, (2-)5-8(-35)-flowered. Flowers are bisexual, papilionaceous, with a 3 mm pedicel. Calyx is tubular, with 2 upper and 3 lower lobes, hairy. Corolla is 5–7 mm long, white, pink,purple or bluish, standard obovate to rounded, wings obovate, keel shorter than the wings. Stamens are 10, 9 fused and 1 free. Ovary is superior, style curved with head-shaped stigma. Fruit is a slightly curved and usually compressed legume 2.5-8(-15) cm × 1-1.5 cm, hairy, dehiscent, 2-3-seeded. Seeds are globose to ovoid or rhomboid, 6-11 mm × 5-8 mm, yellow, green, brown or black, or blotched and mottled in combinations of those colours.

Soya bean is normally self-pollinated and completely self-fertile with less than 1% cross-pollination.