sickle pod

Senna obtusifolia
Shrub
Alternate
Compound
Yellow
Green

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

Common names 
Also known as: Chinese senna,
Family 
Fabaceae
Deciduous 
No
Flowering time 
Autumn- Winter
Native/Exotic 
Exotic
Origin 
This species is thought to be native to southern and eastern USA, Mexico and tropical America
Notifiable 
No
State declaration 
Category 3 - Must not be distributed or disposed. This means it must not be released into the environment unless the distribution or disposal is authorised in a regulation or under a permit.
Council declaration 
As per State Declaration
Known distribution 

Dense infestations occur north of Mackay, south-west of Ingham, and on parts of Atherton Tableland.

Habitat 

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.

Habit 

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.

Impact and control methods 

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.

Stem and leaves 

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 and fruits 

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.

Reproduction and dispersal 

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.

Similar species 

foetid senna (Senna tora), Hairy senna (Senna hirsuta)