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Candle bush (Senna alata)

Candle Bush was probably introduced to Australia as an ornamental and is now recorded across parts of the Northern Territory, New South Wales, Western Australia and Queensland. It forms dense thickets that impede access to waterways and reduce grazing land, and it is suspected of being poisonous to stock.

Key facts

Type: Weed, shrub.

Native to: Tropical South America.

Established in: QLD, WA, NT.

Other names: Ringworm Scrub, Candelabra Plant, Candlestick Senna, Ringworm Bush.

Best time to act: Flowering occurs from June to November, and seedlings germinate in November to December after the wet season’s opening rains.

Identification

  • It is a spreading shrub about 2–3 m high, though it can grow taller.
  • Its leaves are 15–40 cm long and have 8–12 pairs of oblong leaflets.
  • Golden-yellow flowers grow in dense clusters of 20–40, which can be 30–60 cm long.
  • Its straight or curved, compressed-cylindrical pods are 12–16 cm long and have two membranous wings along their length.
  • Look-alike: Popcorn Senna (Senna didymobotrya) is very similar, but its large leaflets have rounded tips and its flower clusters are initially concealed under large purplish-brown bracts.
  • Look-alike: Sicklepod (Senna obtusifolia), Coffee Senna (S. occidentalis) and other similar sennas generally have fewer leaflet pairs than Candle Bush, which has 8–12 pairs in the description.

Where it grows

In Australia it occurs in scattered populations across northern and eastern areas, especially coastal and sub-coastal parts of the Northern Territory and northern Queensland, and grows in sunny, open, perennially moist places such as creek lines, roadsides and drainage channels.

Why it matters

  • It invades native bushland and forms dense thickets.
  • The thickets impede access to waterways and reduce the area available for grazing.
  • It is suspected of being poisonous to stock.

How it spreads

  • It mainly reproduces by seeds, which usually do not fall far from the parent plant, and can also produce suckers when damaged.
  • Water spreads the seeds, aided by pods that can float considerable distances.
  • Seeds can also be carried in mud attached to vehicles, machinery and animals.

Control options

  • Physical control alone is often ineffective because damaged plants can sucker.
  • Seedlings can be dug out if the entire root system is removed.
  • A combination of physical and chemical control may be effective.

Hygiene and washdown

  • Clean mud from vehicles and machinery to avoid carrying seeds to other sites.
  • Check animals and equipment for attached mud before moving them between sites.
  • 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: Declared pest (no control category). Declared pest in WA without a control category, so there is no state-wide control requirement, but movement and keeping rules can still apply.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Declared weed, Class B. Class B: growth and spread must be controlled. All declared weeds are also Class C, so they must not be brought into the NT.
  • 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)
  • 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