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Senna occidentalis

Family

Caesalpiniaceae

Botanical Name

Senna occidentalis (L.) Link

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

Synonyms

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).

Common name

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

Weed

*

Stem

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

Leaves

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.

Flowers

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.

Fruit

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.

Seedlings

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.

Distribution and Ecology

An introduced species probably originating in tropical America but now a pantropic weed. Naturalized in WA, NT, NEQ, 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

All parts of this species are poisonous. (http://www.ces.ncsu.edu/depts/hort/consumer/poiso n/Cassioc.htm)

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).

WA

X

NT

X

CYP

X

NEQ

X

Shrub (woody or herbaceous, 1-6 m tall)

X

RFK Code

3040