Biosecurity Spotters logo

Coffee senna (Senna occidentalis)

Coffee Senna is highly invasive and competes with native plants where it becomes established. It degrades pastures, and its seeds have been reported as toxic to stock.

Key facts

Type: Weed, shrub.

Native to: Tropical and subtropical regions of the Americas.

Established in: QLD, NSW, SA, WA, NT.

Other names: Coffeeweed, Ant Bush, Arsenic Bush, Sickle Pod.

Best time to act: In northern Australia, look for seedlings from the beginning of the wet season and treat them while young; flowering generally begins in mid-summer and continues until April or May.

Identification

  • An upright, short-lived shrub that grows 0.5–2.5 m tall, with reddish-purple stems when young that become greenish brown as they mature.
  • Its compound leaves are 15–20 cm long and have three to five pairs of oval leaflets, with a conspicuous dark gland near the base of each leaf stalk.
  • Bright yellow flowers, 2–3 cm across, grow in small clusters of two to six in the forks of the upper leaves.
  • The flattened, straight or slightly sickle-shaped pods are 8–13 cm long, dark brown with paler edges, and held upright or curving slightly upwards.
  • Each pod contains 20–35 dark brown, flattened seeds.
  • Look-alike: Sicklepod (Senna obtusifolia) has leaflets with rounded tips and pods that curve downwards; Coffee Senna pods are usually flattened and straight or curve slightly upwards.
  • Look-alike: Java Bean (Senna tora) has pods that are almost rounded in cross-section and curve downwards; Coffee Senna pods are usually flattened and straight or curve slightly upwards.

Where it grows

In Australia it is widespread mainly in coastal and subcoastal northern regions, especially coastal Queensland and the Northern Territory, and also occurs in disturbed sites, pastures, grasslands, open woodlands, crops and roadsides.

Why it matters

  • It is highly invasive and competes with native flora where it naturalises.
  • It takes over and degrades pastures.
  • Its seeds have been reported as toxic to stock.

How it spreads

  • Coffee Senna reproduces entirely by seed.
  • Seeds can be dispersed by water or in mud sticking to animals, people, machinery or vehicles.
  • Seeds may also spread as contaminants of agricultural produce.

Control options

  • Control seedlings early, when the plants are readily managed by cultivation or registered herbicides.
  • In crops, pre-emergence herbicides can control germinating seeds.
  • In pastures, reduce grazing pressure and topdress with fertiliser where appropriate to maintain vigorous pasture cover.
  • Control actively growing plants with registered herbicides, following the product label.

Hygiene and washdown

  • Clean mud from boots, machinery and vehicles before leaving infested areas, as seeds can travel in mud.
  • Avoid moving agricultural produce contaminated with seeds.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Declared weed. Weeds Australia lists it as a declared weed in the NT under the Weeds Management Act 2001. Check the NT declared weeds list for its class and what it requires.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources