2. Senna siamea (Lamarck) H. S. Irwin & Barneby, Mem. New York Bot. Gard. 35: 98. 1982.
铁刀木 tie dao mu
Cassia siamea Lamarck, Encycl. 1: 648. 1785.
Trees, 10-15 m tall. Bark gray, subsmooth; young branches ribbed, sparsely puberulent. Leaves 20-30 cm; stipules caducous, linear, tiny; rachis and petiole without glands, puberulent; leaflets 6-10(-15) pairs, oblong or ovate-oblong, 3-7 × 1.5-2.5 cm, leathery, abaxially finely pubescent, adaxially smooth and glabrous, base rounded, apex obtusely rounded, often emarginate, mucronate. Racemes in axils of apical leaves, often several forming a large terminal panicle on a robust peduncle 5-7 cm; bracts linear, 5-6 mm. Sepals suborbicular, unequal in size, outer smaller, inner larger, ca. 9 mm, outside hairy. Petals yellow, broadly obovate, 1.2-1.5 cm, shortly clawed. Stamens 10, among them 7 fertile, anthers opening by apical pores, 2 with filaments ca. 10 mm and anthers 6-7 mm, 4 or 5 with filaments 2-3 mm and anthers 5-6 mm, staminodes ca. 3 mm. Ovary sessile, densely white pubescent. Legume flattened, 15-30 × 1-1.5 cm, suture thick, riblike, pubescent, purplish brown when mature. Seeds 10-30, light brown, ovoid, 2-2.5 × 5-6 mm. 2n = 28.
Cultivated in S China [native to Myanmar and Thailand, and probably also to Cambodia, Laos, and Vietnam; widely cultivated in the tropics].
This tree is planted as an ornamental in parks and gardens and is used as a wayside tree. The hard, durable wood is used for furniture.