Australian Tropical Rainforest Plants - Online edition

Senna occidentalis (L.) Link

Shrub (woody or herbaceous, 1-6 m tall)
Click/tap on images to enlarge
Leaves and flower. © Forest and Kim Starr;
Scale bar 10mm. © CSIRO
Cotyledon stage, epigeal germination. © CSIRO
10th leaf stage. © CSIRO

Link, J.H.F. (1829) Handbuch zur Erkennung nutzbarsten und am haufigsten vorkommenden Gewachse 2 2: 140.

Common name

Weed, Septic; Septic Weed; Senna, Coffee; Coffee Senna; Ant Bush; Negro Coffee


Usually flowers and fruits as a shrub about 1 m tall.


Stipules narrowly triangular, about 2-4 mm long, shed early, leaving only inconspicuous scars. Leaflet blades about 40-70 x 15-25 mm, the terminal pair the largest. About 6-12 leaflets per leaf. Leaflet margins +/- ciliate. A conspicuous raised gland present on the upper surface of the compound leaf petiole shortly above its junction with the twig.


Petals about 13 mm long. Stamens ten, six fertile (two large + four smaller) plus four staminodes. Ovary curved, densely pilose, clothed in white prostrate hairs. Stigma green, recurved.


Pods slightly inflated, about 10-12 x 0.8-1.1 cm, septate. Seeds about 5 x 4 mm, +/- olive green in colour, transverse in the pod. Cotyledons 3-veined.


Cotyledons +/- orbicular, about 11-15 x 9-13 mm. First pair of leaves pinnate, each leaf with about four leaflets, apical pair larger than the lower pair. At the tenth leaf stage: leaf pinnate with about 4-6 leaflets, the rhachis ending in an awl-shaped process. Leaflet blades lanceolate, base oblique, apical pair larger than the lower pair. Leaflet blades about 25-50 mm long. Stipules narrowly triangular, about 3-5 mm long. A raised gland present on the upper surface of the compound leaf rhachis at the point of attachment of the basal pair of leaflets. Crushed leaflets emit an unpleasant odour. Seed germination time 6 to 55 days.

Distribution and Ecology

An introduced species probably originating in tropical America but now a pantropic weed. naturalised in WA, NT, NEQ, CEQ and central Australia and southwards to north-eastern New South Wales. Altitudinal range in northern Australia from near sea level to 800 m. Usually grows as a weed of agricultural land but also found in disturbed areas in rain forest and monsoon forest.

Natural History & Notes

All parts of this species are poisonous.

This species has been suspected to be toxic and cause scouring but there is no conclusive evidence; it is sometimes toxic to rats in laboratory tests. the seeds have been used as a coffee substitute. Also used in Malaysia for medicinal purposes. Hacker (1990).

Cassia occidentalis L., Species Plantarum 2: 377(1753), Type: Herb. Cliff. 159, Cassia no. 7; lecto: BM. Fide J. L. Reveal, Phytologia 71: 454 (1991).
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