Senna siamea

Though it is in the legume family, S. Siamea is not a nitrogen-fixing tree. It is a tropical plant not tolerating temperatures below 20°C well. It will establish in semiarid areas with rainfall as low as 500mm per year, provided there are droughts no longer than 4 to 6 months, and that the roots have access to groundwater. According to Jeff Nugent and Julia Boniface, a good companion tree is Acacia pendula.

Despite its lack of nitrogen-fixing ability, and despite its broad, shallow roots, it is often used in alley cropping. It is a robust coppicer, and will produce a great amount of biomass, yielding up to 500 kg of fresh leaves a year. This production helps it work as a soil conditioner when used as a green manure. Their presence also helps with water infiltration, reducing run-off when planted densely.

S. siamea is is often grown in the service of Santalum species (sandal wood) — usually S. album – which are parasitic trees, tapping into the roots of other plants for water and nutrients. In China, it is used as a host for the lac bug, which is used to produce shellac.

It makes a good fodder for ruminants, but the toxicity of the alkaloids in the plant make it an ill-advised feed for poultry, pigs, and other non-ruminants. Ruminants only, please.

The young leaves and flower buds are boiled two or three times to remove the bitterness and toxicity of the above mentioned alkaloids, and added to curries. It has traditional medical uses that are now discouraged due to the toxicity of the active compound barakol. Still, there is research suggesting anti-cancer properties in S. siamea.

The wood is resistant to termites, and is hard and durable. It also makes an excellent firewood, and charcoal.