Senna italica Seeds | Italian Senna
LATIN NAME: Senna italica
COMMON NAME: Italian Senna
Plant Profile
Italian senna is a low, sprawling shrub of dry plains, rarely more than a metre high and often half that, with stems that radiate outward from a woody base rather than standing up. The leaves are pinnate with four to six pairs of small, grey-green, oval leaflets, and they fold shut at dusk and open again in the morning — a habit shared across the genus. The flowers are yellow, five-petalled and borne in short axillary racemes, opening a few at a time over a long season, and they are followed by flat, papery pods that turn brown and rattle when the seed is ripe. It ranges from Senegal across the Sahel and the Horn of Africa through Arabia to Iran, Pakistan and India, always on light, warm, sharply drained ground, and it has been carried as a minor crop and a wayside plant into the Americas and Australia.
Science & Biotechnology
The plant’s chemistry is its identity. Leaves and pods carry the dianthrone glycosides sennoside A and B, which pass through the small intestine intact and are hydrolysed by colonic bacteria into rhein anthrone, the compound that stimulates the large bowel. That is the same mechanism as the official senna of the pharmacopoeia, Senna alexandrina, and S. italica has been used as a local substitute and, in the herb trade, sometimes as an adulterant. It is worth knowing that Senna sits in the Caesalpinioideae, a group in which nodulation is largely absent, so unlike a pea or a clover this shrub does not fix nitrogen and should not be sold as a soil improver. Recent work has also looked at its leaf extracts for antifungal and antioxidant activity, though none of that has changed the pharmacology of the pods.
Uses & Benefits
Its practical use is as a laxative, and that use is old, widespread and genuinely effective — which is exactly why it deserves respect rather than enthusiasm. The pods are the strongest part and the leaves milder; a tea of a few pods is the traditional dose, and it should not be taken habitually, in pregnancy, or alongside other medicines without advice, because chronic anthraquinone use causes dependence and electrolyte loss. In the garden the plant is a modest, cheerful thing for a hot dry bank, a gravel garden, or the front of a border in a Mediterranean climate, where its long succession of small yellow flowers and blue-green foliage earn their place. In the Sahel the young growth is browsed by goats and camels, though mature plants are largely left alone once the pods have formed.
Growing from Seed
Senna seed has a hard coat and germinates best after a hot-water soak: pour water just off the boil over the seed, leave it for twelve hours, and sow the swollen ones. Surface-sow on a gritty, free-draining mix, cover lightly, and keep at 22 to 28 °C in good light; germination takes one to three weeks. The seedlings are fast and a little leggy, so pinch them once and pot them on steadily. Plant out after the last frost in full sun, on ground that drains sharply, and water through the first summer only. In a cold climate treat the plant as a half-hardy annual or overwinter it under glass, since it takes several degrees of frost at the root. Light pruning in early spring keeps the shrub compact and stops it from sprawling over its neighbours.
Our Take
A useful plant with a real pharmacological punch, best grown for its yellow spikes and treated as medicine only with care.
Related Reading
More species in the same orbit as Italian Senna: