Senna siamea (Lamk) Irwin & Barneby

Senna siamea (Lamk) Irwin & Barneby




Cassia siamea Lamk, Cassia flori­da Vahl, Senna sumatrana (Roxb. ex Homem.) Roxb.

Vernacular Names


Johor, sebusok, guah hitam.


Siamese senna, kassod tree, Thailand shower.


Johar (gen­eral), bujuk, dulang (Sumatra).






'khi:z hlek.


Khilek (general), khilek-Iuang (northern), khilek-yai (cen­tral).


C[aa]y mu[oof]ng den, mu[oof]ng xi[ee]m, humbo (Thuan Hai).

Geographical Distributions

Senna sia­mea is native to South and Southeast Asia, from Thailand and Burma (Myanmar) to southern In­dia and Sri Lanka. However, it has been cultivat­ed for so long, that its exact origin is unknown. It is widely planted throughout the tropics and is lo­cally naturalised.


Senna siamea is a tree that can reach up to 6-12(-30) m tall. The spreading branches form a dense rounded crown. The bark is almost smooth, grey and with ribbed young shoots.

The leaves are simply paripinnate, oblong-ellipti­cal in outline and measure 10-35 cm long. The stipules are subulate, measure 1 mm long and very early caducous. The petiole is cylindrical but with a shallow ventral groove that is 1.5-3.5 cm long and glandless. The rachis is 4.5-25 cm long and glandless. The peti­olule is 2-4 mm long. The leaflets are in 4-16 pairs, subcoria­ceous, oblong to ovate-oblong, measuring 3-8 cm x 1-2.5 cm, 2-4 times as long as wide, with unequal-sided rounded to wedge-shaped base, rounded to retuse or blunt at apex, often mucronate, glossy and hairless above, dull and rough to delicately hairy be­low.

The inflorescence is erect, terminal, 10-60-flow­ered, panicle leafy, measures 15-60 cm long and composed of numerous dense corymbs measuring up to 10 cm x 5-6 cm. The peduncle is 5-7 cm long and robust. The bracts are obovate in the lower half and suddenly narrow to become linear and acute for 3-6 mm long. The bracts are hairy but early caducous. The bracteoles are absent. The pedicel is 2-3.5 cm long. The 5 sepals are unequal, rounded-ovate, measure 4-9 mm long, thick, hairy, repanding-reflexed and long persistent. The 5 pe­tals are orbicular-obovate, measure 1-2 cm long, yellow, hairless while the upper part is with claw 1-2 mm long. There are 10 sta­mens where the 3 lower ones are with filaments 6 mm long and anthers 5 mm long. The other 3 upper ones are staminoidal while the 4 meridian ones are with filaments 3-4 mm long and anthers 5 mm long.

The ovary is shortly hairy, and with style 4-5 mm long, while the stigma is in the form of a dot. The pod is flat­tened, 20-30-seeded, measuring 15-30 cm x 12-16 mm, al­ternately bulging and depressed in the centre, with thick rim, slightly hairless, dull and finally dehiscent. The seed is very flat ovoid, measuring 6.5-8 mm x 6 mm, light brown and glossy. The areole is oblong-elliptical measuring 3-4.5 mm x 1 mm.

Ecology / Cultivation

Senna siamea can grow in a range of cli­matic conditions, but is particularly suited to the lowland tropics with a monsoon climate with a mean annual rainfall of 500-2800 mm, optimally about 1000 mm. Under semi-arid condi­tions (500-700 mm), S. siamea will only grow when its roots have access to groundwater. It re­quires a mean minimum temperature of 20°C, ranging from 14-28°C, and a mean maximum temperature of 31°C, ranging from 24-36°C. The maximum length of the dry period should not ex­ceed 4-8 months. It is susceptible to cold and frost and does not do well at altitudes above 1300 m. Light requirements are high. S. siamea performs best on deep, well-drained, fertile soils with pH 5.5-7.5, but will grow on de­graded, lateritic soils but provided drainage is not im­peded. It grows poorly on infertile, poorly drained podzolic soils. It is not tolerant of salinity, but is reasonably tolerant of acid soil conditions.

Line Drawing / Photograph



  1. Plant Resources of South-East Asia No.11: Auxiliary plants.