Senna siamea

Author: (Lamarck) Irwin & Barneby

Naves in Blanco, Fl. Filip., ed. 3 (1877-83) t. 426

Morphological description (siamea Senna lf/infl FT27 )
Tree up to c. 15 m; young branches pubescent, finely striate. Stipules tiny, subulate, caducous.

Leaves (siamea Senna general 386532) paripinnate with 7-10(-15) pairs of leaflets; petiole 2-3 cm; rachis 10-25 cm. Leaflets ovate-oblong, 3-7 by 1-2 cm; rounded or emarginate, at apex with a short mucro, rounded at base; glabrous on upper surface, finely pubescent below.

Inflorescence (siamea Senna general 386532) large, terminal panicles on a robust, 5-7 cm long peduncle; bracts obovate, long acuminate, c. 5 mm; bracteoles absent; pedicels 2-3 cm, velutinous.

Flower: Sepals 5, orbicular, unequal, velutinous outside, the two outer c. 5 mm, the inner up to 9 mm. Petals 5, yellow, oblong-obovate with a short claw, l.5-2 cm. Stamens 8-10: 2 with filaments c. 10 mm and anthers 6-7 mm with apical dehiscence; 4-5 with filaments 2-3 mm and anthers 5-6 mm; 2-3 staminodes c. 3 mm; filaments of all stamens straight. Ovary densely velutinous; style glabrous; stigma inconspicuous.

Pods (siamea Senna general 386532 ) flattened, alternately expressed and depressed over the seeds giving a 'wavy' surface; sutures thick, rib-like, 20-30 by 1-1.5 cm.

Seeds 20-30, ovate, light brown 20-25 by 5-6 mm.

Indigenous to Burma, Thailand and probably Cambodia, Laos and Vietnam. It is widely planted throughout the tropics.

Habitat & Ecology
In various types of forests at low altitudes. Flowering throughout the year.

Planted as ornamental in parks, gardens and frequently used as wayside tree up to 1000 m altitude. As a rapid growing species it is also appreciated for use as shade trees and windbreak in e. g. coffee plantations. It is sometimes running wild but hardly occurs as truly naturalized. Locally used for medicinal purposes. See Heyne (1950: 747); Burkill (1935: 480).