hairy cassia

Senna hirsuta
Herb
Alternate
Compound
Yellow
Green

Senna hirsuta is a large upright (erect) herbaceous plant, or somewhat long-lived (perennial) shrub, becoming slightly woody with age and growing 0.5-3 m tall. The stems, leaves and pods are all densely covered with long pale greyish-white coloured hairs. Its stems are usually also ridged lengthwise (longitudinally)

Common names 
Also known as: Hairy senna, shower tree senna, sicklepod, glaberrima senna, stinking cassia, woolly senna, woolly wild sensitive plant,
Family 
Fabaceae
Deciduous 
No
Native/Exotic 
Exotic
Origin 
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 

Cassia hirsuta is naturalised in north-eastern Australia

Habitat 

A weed of disturbed sites, waste areas, roadsides, riparian zones (banks of watercourses), plantation crops, forest margins, open woodlands, pastures, grasslands and coastal environs in tropical and subtropical regions.

Habit 

There are seven ‘varieties’ of Senna hirsuta. All varieties are annual or short-lived perennial herbs that become softly woody with age (generally 0.3–2.4 m tall). Depending on variety, the species may be erect or diffuse, simple or multiple-stemmed. Pubescence and pod features vary considerably and these attributes are used as a key to differentiate varietiesl

Impact and control methods 

Invades disturbed areas such as roadsides, fence lines, creekbanks, grazed pastures and rainforest edges.

Stem and leaves 

The compound (pinnate) leaves are alternately arranged along the stems and borne on ribbed stalks (petioles) 40-65 mm long. These leaves (10-25 cm long) have two to six pairs of large leaflets (40-105 mm long and 20-40 mm wide), with those further from the leaf stalk usually being noticeably larger. The leafletsare egg-shaped in outline with broad end at base (ovate) or oval (elliptic) in shape with pointed tips (acute or acuminate apices) and entire margins. As noted earlier, the leaf surfaces are covered in greyish-white hairs (they are densely pubescent). There is also a small cone-shaped projection (conical gland) present near the base of each leaf stalk (petiole).

Flowers and fruits 

The yellow to deep orange-yellow irregular flowers are borne in small unbranched clusters in the upper leaf forks or at the tips of the branches (in terminal or axillary racemes). These clusters usually contain only 2-8 flowers, each flower being borne on a stalk (pedicel) 10-25 mm long. The flowers have five petals (8-16 mm long) which may become conspicuously brown-veined as they mature. They also have five sepals (6-8 mm long) and six or seven fertile stamens with anthers 3-8 mm long.

The fruit is a slightly sickle-shaped (falcate) brown pod that is usually curved downwards (recurved). These pods (10-18 cm long and 4-6 mm wide) are very slender, slightly flattened and septate, and densely covered in long whitish-coloured hairs (they are densely pubescent). They turn brown as they mature and are slightly indented between each of the seeds (faintly septate). The seeds are ovoid to rounded in shape (globular), seed surface is smooth, seed ranges in colour including olive, brown, or black.

Reproduction and dispersal 

This plant reproduces by seed only. The seeds are probably dispersed by water and animals that eat the pod(fruit). They may also be spread as a contaminant of agricultural produce or in mud sticking to animals, footwear, machinery and vehicles.

Similar species 

Senna hirsuta is very similar to S. obtusifolia (sicklepod), S. occidentalis (coffee senna), and S. septemtrionalis (smooth senna).