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Senna spectabilis (DC.) H.S.Irwin & Barneby 1982
pronounced: SEN-nuh speck-TAB-ih-liss
(Fabaceae — the pea family)
subfamily: Caesalpinioideae – the cassia subfamily
synonym: Cassia spectabilis DC. 1813
pronounced: KASS-ee-uh speck-TAB-ih-liss
common name: Spectacular Cassia
Senna is the Latin form of an Arabic word for a thorny bush; spectabilis is Latin for ‘worth seeing’. Quite a few trees that were formerly members of the Cassia genus have now been moved into Senna, although not all authorities recognize the changes.
The tree photographed is on the corner of Picnic and Magnetic Streets. There are quite a number of these trees on the island, including several in Wansfell Street, Picnic Bay, and on the roadside in Sooning Street, Nelly Bay. The one photographed is quite a straggly, leggy tree, and certainly would have benefitted from some pruning when it was younger, to give it a more attractive shape. Younger trees nearby, descended from it, are even more straggly. However, it is a beautiful sight when in full bloom, usually in the April – May period.
Senna spectabilis is evergreen in the tropics, but may shed its leaves in cooler climates. It can grow up to 10 m or more in height, and the trunk up to 30 cm in diameter, with a spreading crown. The bole is short, tending to fork near the ground, and the tree is wide-spreading with drooping leafy branches. The bark is smooth, grey with horizontal markings, with many warts and short fissures, rougher with age.
The leaves are alternate, up to 40 cm long, pinnate with up to 19 pairs of leaflets, each up to 7 cm or so long. The leaflets are narrowly elliptic with a rounded base, an acute apex and an entire margin. The upper surface of the leaflets is glabrous and dull green, with many sunken side veins. The lower surface is a dull light green, and may either bear some soft hairs, or be hairless.
The inflorescence is large, terminal, with lateral leafy panicles, up to about 50 cm long. There are many fragrant flowers in each inflorescence, with orange-yellow sepals and yellow petals fading to whitish with age. The fruits are green cylindrical (or sometimes flattened) pods, ending in a short, narrow point, hard, either not splitting open at all, or opening slightly on one side. They can grow up to about 30 cm long. They turn blackish brown, and the seeds are in separate compartments. There are anything up to 50, or even more, seeds in each pod, flattened, brown, about 5 mm in diameter, with papery septa.
The tree provides good forage for bees. In many areas in Central America and the Caribbean, the timber is used for firewood and for making both charcoal and tool handles. The timber is heavy, durable, and termite-resistant.
Both senna leaves and pods were used in ancient Arabian medicine as safe and effective laxatives. Today, senna is still recognized as one of the most popular and reliable stimulant laxatives.
Information about medicinal qualities of plants, or about their use as medicines, is for interest only, and is not intended to be used as a guide for the treatment of medical conditions.
Photographs taken at Picnic Bay 2009
Page last updated 11th February 2017