The morphology of S. occidentalis as described by Parsons and Cuthbertson (1992) for Australia and Henderson (2001) for South Africa, closely matches that given for the plant in other parts of the world. It is a low growing, sparsely branching annual or short-lived perennial plant up to 0.5-2 m high and having a characteristic foetid odour. The stems are reddish purple, erect, 4-angled when young, becoming rounded with age. The plant has a robust primary root with several laterals. The leaves are pale green on reddish stalks;alternate, pinnate, with 3-5 (sometimes 6) pairs of opposite ovate to lanceolate-elliptic leaflets, 25-100 mm long, 20-30 mm wide, rounded at the base. A conspicuous, dark-coloured gland occurs at the base of the petiole (leaf stalk) but not on the stalks of the leaflets. The flowers are pale to bright yellow, 20-30 mm in diameter, in 2-6 flowered axils of the upper leaves;sepals are red veined;5 petals per flower, the 2 anterior ones are smaller than the others;fertile stamens 6, the two basal ones longer than the rest, 4 infertile stamens are reduced to tiny petal-like staminodes. Further descriptions of the floral anatomy of S. occidentalis and nine other species of Cassia are given by Chhavi-Thakur and Thakur (1988). The fruit is a dark brown, flattened, sickle-shaped pod with paler stripes along the edges when mature. Pods are 75-130 mm long, 8-10 mm wide, containing a single row of 25-35 seeds. The seeds are dark brown, flattened, hard, 5 mm long and 3 mm wide.
Related invasive species
- Senna occidentalis
Related Farm Practice
- Flora
- Pastures
- Rest
Related location
- South Africa
S. occidentalis is an annual to short lived perennial herb to small shrub with a pantropical distribution (PROTA, 2016). It is reported as invasive throughout Oceania, and various countries in Asia and Africa, where is reported as introduced (BioNET-EAFRINET, 2016;PIER, 2016). Within its native range S. occidentalis is listed as invasive for Cuba by Oviedo Prieto et al. (2012).
This species is recognised as an invasive herb or a problematic weed that affects crops and plantations all over its range (PIER, 2016). For example, in the Northern Territory, Australia, it is a class B declared weed, i.e. spread to be controlled in all of the Territory (Flanagan, 1998). This weed is a problem in seven states of the USA and is increasing in eight others (Teem et al., 1980). Its ability to colonize a wide range of climatic and edaphic conditions is epitomized by its occurrence in East Africa where it is found at altitudes of 0-1740 metres above sea level (Brenan, 1967). Though probably less important than the related weeds, S. obtusifolia and S. tora, S. occidentalis has the potential to become a weed of more widespread significance. In the USA it is on the regulated invasive list for Florida (Invasive Plant Atlas of the United States, 2016).
S. occidentalis is commonly cited as a weed of soyabean, groundnut, cotton and pastures (Teem et al., 1980). However, its distribution indicates that it is likely to occur as part of the mixed weed flora of many annual crops in the tropics and subtropics (PROSEA, 2016;PROTA, 2016)..