sickle pod
Senna obtusifolia is a short-lived (annual or biennial) shrub growing to up to 2.5 m tall, but usually less than 2 m in height. The lower stems often sprawl along the ground in open areas.
Plants produce numerous, branched, sprawling stems that are 1.5-2 m long. These stems are usually softly hairy (pubescent) when young, but become mostly hairless (glabrescent) with age. The foliage has a slightly rank odour
Dense infestations occur north of Mackay, south-west of Ingham, and on parts of Atherton Tableland.
Senna obtusifolia is a weed of disturbed sites, waste areas, roadsides, riparian zones (banks of watercourses), floodplains, drainage channels, open woodlands, fallow land, crops and pastures in wetter tropical and subtropical environments. It usually grows as a pasture weed but is sometimes found along roads and in disturbed areas in rain forest.
Sicklepod is a vigorously growing, very competitive woody shrub which grows 1.5−2.5 m tall and 1 m wide. It is normally an annual, but plants which have been slashed or have survived chemical treatment often reshoot, flower and last for another year.
These species can invade and completely dominate pastures and other disturbed areas such as roadsides, fence lines, creek banks and disturbed areas. They have the potential to become major weeds of many crops within a matter of two or three growing seasons.
Leaves are divided into three opposite pairs about 4 cm long and 2 cm wide, rounded at the end and wedge-shaped at the base.
Flowers are yellow, small, about 1 cm across and have five petals. The seed pod is long (10−15 cm), slender (3−5 mm wide) and sickle-shaped. When ripe, the pods burst open, shedding their shiny, flattened, dark brown seeds.
This species reproduces by seed only. This plant spreads by reseeding itself. Seeds are dispersed by water and animals that eat the fruit (e.g. cattle). They may also be spread as a contaminant of agricultural produce (fodder and pasture seeds) or in mud sticking to animals, footwear, machinery and vehicles.
foetid senna (Senna tora), Hairy senna (Senna hirsuta)
