Common Name: Siamese senna. Tamil Name: Manjal konnai
Siamese senna is a tree that grows to about 15 meters in height. The native of this tree is not well established: but likely to be of Asian origin. The leaves are pinnate, the rachis is rusty is color when young- the young leaflets are also rusty in color. The rachis can be as long as 25 cm. About 9-10 pairs of leaflets are seen. The leaflet stalk and leaflet measure around 3 mm and 3 cm respectively. The leaves are shinning green and ovate in shape with a rounded apex and bottom. The inflorescence is in the form of a axillary panicle of corymbs. The flower stalk and flower length measure around 2.5 cm and 3.5 cm respectively. The flower has distinct 5 clawed distinct yellow petals. The petals are obovate in shape and measure around 2 cm each. The flower encloses 10 stamens and a single style. The fruit is in the form of a green pod which turns dark brown in color on maturity. The pod measurers around 20 cm in length. The pod is constricted between the seeds. The pod bears several seeds which are shinning black in color, flat in appearance, ovate in shape and measure around 1 cm in length. Siamese senna is one of the most popular avenue and garden tree in India. It is often confused with Senna spectabilis- there is a need to distinguish between the two as S spectabilis is highly invasive. The leaf and pod structure of these two trees are different-please refer to the photographs enclosed. Siamese senna is the larval host plant for Common Shot silverline, Lemon emigrant and Common grass yellow butterflies.