Quick Facts

Quick facts

• Coffee Senna (Senna occidentalis) is a short lived shrub with yellow flowers that is a native of tropical Americas.
• It competes with native flora and takes over and degrades pastures.
• The seeds are reported as toxic to stock.
• Coffee Senna is widely naturalised in the coastal and subcoastal regions of northern Australia.
• The young plants develop rapidly, attaining a height of 1 m in just a few weeks.

What Does It Look Like?

What is it?

Coffee Senna (Senna occidentalis) is an upright and short lived shrub growing to 0.5–2.5 m tall. The stems are sparsely branched, smooth and hairless or sparsely hairy. They are reddish purple in colour and somewhat four-angled or grooved when young, but turn greenish brown and become rounded as they mature. The alternately arranged, compound leaves (leaves divided into leaflets) are 15–20 cm long, borne on reddish leaf stalks to 3–5 cm long. They are composed of three to five oppositely arranged leaflets which are 3–10 cm long and 2–3 cm wide and egg-shaped to oval. These leaflets have smooth leaf margins and pointed tips. There is a conspicuous dark coloured gland near the base of each leaf stalk.

The bright yellow flowers are 2–3 cm across and have five petals, 1–1.5 cm long, which are borne in small clusters of two to six in the forks of the uppermost leaves. These flowers have six stamens (stalks or filaments containing pollen) and four tiny petal-like structures at their centres.

The fruit is a flattened and slightly sickle shaped or almost straight pod, 8–13 cm long and 8-10 mm wide. These pods are held upright or curve slightly upwards. They are dark brown with paler edges, and each contains 20–35 seeds. The seeds are dark brown, flattened, and about 5 mm long and 3 mm wide (Navie 2004). For further information and assistance with identification of Coffee Senna, contact the herbarium in your state or territory.

Flower colour

Yellow

Growth form (weed type/habit)

Shrub

Where it currently grows? Preferred habitat

Coffee Senna prefers roadsides, waste areas, disturbed sites, pastures, grasslands, open woodlands, coastal environs and crops in tropical, subtropical and semi-arid regions (Parsons & Cuthbertson 2001; Navie 2004).

Are there similar species?

Hairy Senna is very similar to Sicklepod (Senna obtusifolia), Java Bean (S. tora), Coffee Senna (S. occidentalis), Smooth Senna (S. septemtrionalis) and the Native Arsenic Bush (S. planitiicola). It is also relatively similar to Easter Cassia (S. pendula var. glabrata), Pepper-leaved Senna (S. barclayana), Candle Bush (S. alata), Popcorn Senna (S. didymobotrya) and Sesbania Pea (Sesbania cannabina var. cannabina). These species may be distinguished from Hairy Senna by the following differences (Navie 2004):

• Hairy Senna is a relatively small slender shrub (usually 0.5-2 m tall) that has moderately sized leaves with several (3-6) pairs of leaflets. The relatively large leaflets are comparatively broad and have pointed tips. Its pods are usually somewhat flattened, straight or slightly curved and are densely covered in long hairs (Navie 2004).
• Sicklepod has relatively large leaflets that are comparatively broad and have rounded tips. Its pods are curved downwards and are mostly hairless. Java Bean has moderately-sized leaflets that are comparatively broad and have rounded tips. Its pods are almost rounded in cross-section, are curved downwards and are mostly hairless. Coffee Senna has pods that are usually somewhat flattened. These pods are straight or slightly curved upwards and are mostly hairless (Navie 2004).
• Smooth Senna, Pepper-leaved Senna and Native Arsenic have pods that are almost rounded in cross-section and mostly hairless. Easter Cassia has moderately-sized leaflets that are relatively broad, have rounded tips and have prominent yellowish coloured margins. Its pods are hairless (Navie 2004).
• Candle Bush has very large leaves with numerous (8-14) pairs of leaflets. The large leaflets are relatively broad (20-50 cm) and have rounded tips. It has very large elongated pods which are four-angled in cross-section and winged. These pods are mostly hairless (Navie 2004).
• Popcorn Senna has large leaves with numerous (7-18) pairs of leaflets. The relatively large leaflets are relatively broad and have rounded tips. The relatively large pods are flattened in cross-section and mostly hairless (Navie 2004).
• Sesbania Pea has moderately sized leaves with numerous (12-30) pairs of leaflets. The relatively small leaflets are very narrow and have rounded tips. Its very elongated pods are rounded in cross-section and mostly hairless (Navie 2004).

Why Is It A Weed?

What are its impacts?

Native ecosystems: Coffee Senna is highly invasive and it competes with native flora in areas that it naturalises.

Agriculture: It degrades pastures and has been reported as toxic to stock (Parsons & Cuthbertson 2001; Smith 2002).

How does it spread?

Coffee Senna reproduces entirely by seed. Seeds are dispersed by water or in mud sticking to animals, humans, machinery or vehicles. They may also be spread as a contaminant of agricultural produce (Navie 2004).

What is its history in Australia?

It is unknown how, when and why Coffee Senna arrived in Australia but it is recorded as growing in the Royal Botanic Gardens, Sydney in 1908 (National Herbarium of New South Wales 2008).

How To Manage It?

Best practice management

Chemical control: Coffee Senna is controlled easily by cultivation or with herbicides when in the seedling stage. In crops, pre-emergence herbicides give good control of germinating seeds. In pastures where there is a lot of bare ground, it is essential to establish a vigorous cover by reducing grazing pressure, topdressing where appropriate, and at the same time controlling emerging seedlings with herbicides (Parsons & Cuthbertson 2001).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Non-chemical control: Pasture management: In pastures, where Coffee Senna quickly invades bare and trampled areas, it is essential to maintain a vigorous pasture cover by reduced grazing pressure and top dressing with fertilizer where appropriate, while at the same time, controlling the actively growing weed with herbicides (Parsons and Cuthbertson, 2001, CABI 2016).

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

In Northern Australia, Coffee Senna seeds usually germinate at the beginning of the wet season, but some may germinate at any time of the year, particularly in coastal Queensland, provided moisture is available. The young plants develop rapidly, attaining a height of 1 m in a few weeks. Flowering commences in mid-summer and continues until April or May when most plants die. Plants in warmer, moist situations may persist for another season. Seeds germinate over a wide temperature range and seedlings emerge from a depth of up to 12.5 cm (Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

NSW, NT, QLD, SA, VIC, WA

What areas within states and territories is it found?

Coffee Senna is a widespread species that is found mainly in the coastal and subcoastal regions of northern Australia, most commonly in the coastal districts of Queensland and the Northern Territory. It has a scattered distribution in the northern parts of Western Australia and in the inland regions of Queensland and the Northern Territory. It has also been recorded as occurring in New South Wales, Victoria, South Australia and in the southern parts of Western Australia (Navie 2004).

Where does it originate?

Coffee Senna is native to the tropical and subtropical regions of the Americas (Navie 2004).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NT, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Senna occidentalis

Other scientific names (synonyms)?

• Cassia occidentalis L.
• Cassia occidentalis L. var. occidentalis

Does it have other known common name(s)?

Coffeeweed, Ant Bush, Arsenic Bush, Sickle Pod, Nigerian Senna, Negro Coffee, Stink Weed, Stinkweed, Stinking Pea, Stinking Weed, Septicweed