Senna hirsuta (L.) Irwin & Barneby

Senna hirsuta (L.) Irwin & Barneby

Family

Leguminosae 

Synonyms

Cassia hirsuta L., Cassia  lepto­carpa Benth.

Vernacular Names

Geographical Distributions

Senna hir­suta is a native of tropical America and is now dis­tributed throughout Malaysia, Indo-China, Thai­land and most countries in the Asian and African tropics. In Java, where it has long been known and has naturalised, it is more common in West Java than towards the east.

Description

Senna hir­suta is an erect or diffuse, simple or several­-stemmed herb that can grow up to 2.5 m tall. It becomes soft woody with age, with a fetid smell, and hairy but high­ly diverse in pubescence. The twigs are grooved, ribbed and densely hairy.

The leaves are 10-20 cm long and simply paripinnate. The stipules are linear-acute, measure 3-15 mm long and usually not persistent. The petiole is stout, up to 6.5 cm long, villose, and above the insertion with a ses­sile, oblong gland. The rachis is 3-16 cm long and glandless. The petiolules are up to 3.5 mm long, slender, villose and of­ten not opposite. There are 2-8 pairs of leaflets which are strongly accrescent distally, chartaceous, lance-shaped-acum­inate, and measuring 2-12.5 cm x 1-5 cm. They are 2-6 times as long as wide, slightly unequal-sided, with acute or round­ed base, dark green and roughly villose on both surfaces.

The inflorescence is an axillary or rarely terminal, 2-8 ­flowered raceme (up to 45 in South America), measures 1(-8) cm long and aggregate in leafy panicles. The pedun­cle is up to 3 cm long. The bracts are linear to lance-shaped, measure 1.5-5 mm long and early caduceus. The bracteoles are absent. The pedicel is 1-2.5 cm long and pubescent. There are 5 sepals which are un­equal. The 2 outer ones are small, orbicular, measure 4-7 mm long and hairy while the other 3 inner ones are larger, measure 7-10 mm long and partly hairless. There are 5 petals which are unequal, obovate, measure 8-28 m long, yellow, hairless and short-clawed. There are 10 stamens. Two of them are large with flat filaments 4-7 mm long and curved anthers 7-8 mm long that open by apical pores. The rest of the 8 stamens are smaller and staminoidal. The ovary is woolly and recurved. The style is short, hairless and with hairy subapical stigma.

The fruit is a falcate to straight angular pod, measuring 6-28 cm x 3-7 mm, septate, 50-90-seeded and stiff hairy. The seed is slightly compressed, orbicular, about 3 mm in di­ametre and dark olive coloured. The areole is 0.5-2.5 mm long and narrowly ellip­tical.

Ecology / Cultivation

In Southeast Asia, Senna hirsuta is found in plains and hilly areas up to 700 m alti­tude. It grows spontaneously in waste locations, along roadsides, railway embankments, dry ditch­es and in secondary forests. It is found in gardens and fields as a weed and prefers open locations.

Line Drawing / Photograph

References

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