Siam-bean

Cyamopsis tetragonoloba, the guar or cluster bean, is an erect, drought-tolerant annual legume of the family Fabaceae, of probable south Asian origin and cultivated since antiquity in India and Pakistan and more recently in arid parts of the United States, Sudan and Australia. The plant grows 60 centimetres to 2 metres tall, with a stout, finely pubescent, often purple-tinged main stem branching from near the base. Leaves are alternate, trifoliolate, with ovate to rhomboid, coarsely toothed leaflets 4 to 10 centimetres long and prominent stipules. Small, pale pink to violet pea-like flowers about 8 millimetres long are borne in dense, short axillary racemes. The fruits are short, straight, four-angled pubescent pods 4 to 10 centimetres long, borne in characteristic dense clusters at the upper nodes, each containing five to twelve small, hard, pale grey to greyish-brown seeds whose endosperm is exceptionally rich in galactomannan polysaccharide, the source of commercial guar gum.