Senna siamea

Senna siamea is a medium-sized (10-15 meters) deciduous tree. It has usually a short and straight bole and a dense and spreading crown.

Senna siamea has a straight and short trunk usually reaching no more than 30 cm in diameter.
Its bark is smooth, greyish and slightly fissured longitudinally with age.

The leaves of Senna siamea grow alternately on the stem (spirally arranged).
Senna siamea has compound leaves : paripinnate leaves.
The leaf is 15-30 cm long and 6-12 cm wide.
The leaves have a 3-4 cm long petiole with a pair of caducous and subulate stipules at the axil of the stalk.
The rachis is slender, reddish coloured above and green beneath.
There are 7-12 pairs of chartaceous leaflets, dark green coloured on the upper side and pale light green beneath. They are glabrous on both sides (some minute hairs on the nerves beneath). The leaflets are ovate-oblong with a rounded base and an obtuse (somewhat emarginate) apex tipped with a minute sharp mucro. The margins are entire, orange-reddish coloured. On the lower side, the midrid is prominent and orange-reddish coloured too.
The leaflets have a 3 mm long petiolule.
The venation of the leaf is reticulate.

The inflorescence of Senna siamea is a terminal panicle. These panicles are pyramidal and erected at the end of twigs. These large inflorescences (up to 30 cm long and 15 cm wide) are composed of numerous bright yellow flowers.
The flowers are 3 cm across with a 2.5 cm long and hairy pedicel.
The calyx is composed of 5 hairy, yellow-greenish coloured and ovate lobes and a calyx-tube. The calyx lobes are 6-7 mm long and 4-5 mm wide, concave and ovate with an obtuse apex.
The corolla is composed of 5 bright yellow petals. These petals are obovate, clawed and with an obtuse apex. They are 1.3-1.5 cm long and 0.8-1 cm wide. The calyx is glabrous.
The androecium is composed of 10 stamens of different sizes, from 4 mm to about 1.5 cm long. The filament are thick and straight and about the twice as long as the anthers. The anthers are erected, basifixed and brownish coloured. The smaller are 2 mm long and the longer about 7 mm.
The ovary is superior, linear and grooved, 1 cm long and pubescent. The style is linear, curved, glabrous and 4-5 mm long.

The fruit of Senna siamea is a long, flat and narrow pod.
It is 20-25 cm long and 1 cm wide, woody and dark brown when ripe.
These pod contains numerous seeds.

The seeds of Senna siamea are flat, smooth, glossy and brown coloured with a distinct areola.
These seeds are oblong, 8 mm long and 5-6 mm wide.
There are 15-20 seeds in a pod.

The leaves of Senna siamea are used as green manure to improve the soil quality.

Senna siamea can be planted to limit erosion : the tree increase water infiltration in the topspoil, reducing runoff and soil erosion.

The dense wood of Senna siamea makes good fuel and it gives an excellent charcol.
The wood of Senna siamea was formerly used for locomotive engines.

Senna siamea is grown as a shade tree along roads and in cocoa, coffee and tea plantations.

The tree is often planted as an ornamental for its abundant shiny yellow flowers.

In India, the species is used as a host for the parasitic and well-known aromatic sandalwood (Santalum spp.).

Senna siamea is also used extensively for rehabilitation of degraded land (as aluminium mine tailings).

Source : Orwa C, A Mutua, Kindt R , Jamnadass R, S Anthony (2009) Agroforestree Database : a tree reference and selection guide

The leaves and seeds are eaten by cattle and sheep but are toxic to non-ruminants. (Trees of Delhi, P. Krishen)

Senna siamea yields a medium-weight to heavy hardwood. The heartwood is black-brown with paler streaks (it is known as "Bombay blackwood") and the sapwood is pale. This hard and durable wood is resistant to termites. The nicely figured wood is used for joinery, furniture making, inlaying, handles, sticks and for making many decorative objects. The wood is also used for building.

All the parts of plants are rich in tannins, they can be used for tanning. Highest tannin concentration is found in the leaves.

Sennna siamea is used in China as a host plant for the lac insect (Kerria lacca) to produce the resin known as lac or shellac.

Source : Orwa C, A Mutua, Kindt R , Jamnadass R, S Anthony. 2009 Agroforestree Database : a tree reference and selection guide

In Thailand, the young fruits and leaves are eaten as a vegetable. During preparation the cooking liquid is replaced 3 times to remove toxins.

In Sri Lanka, the flowers and young fruits are used in curries.

Source : Orwa C, A Mutua, Kindt R , Jamnadass R, S Anthony. 2009 Agroforestree Database : a tree reference and selection guide

The fruits and the roots of Senna siamea are used to treat intestinal worms.