Senna siamea (Lamk) Irwin & Barneby
Family
Leguminosae
Synonyms
Cassia siamea Lamk, Cassia florida Vahl, Senna sumatrana (Roxb. ex Homem.) Roxb.
Vernacular Names
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Malaysia |
Johor, sebusok, guah hitam. |
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English |
Siamese senna, kassod tree, Thailand shower. |
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Indonesia |
Johar (general), bujuk, dulang (Sumatra). |
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Philippines |
Robles. |
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Cambodia |
‘ângkanh’. |
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Laos |
‘khi:z hlek. |
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Thailand |
Khilek (general), khilek-Iuang (northern), khilek-yai (central). |
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Vietnam |
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.
Description
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
References
- Plant Resources of South-East Asia No.11: Auxiliary plants.
