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Green cestrum (Cestrum parqui)

Green cestrum is an introduced weed in Australia that is toxic to livestock and humans. It can invade native ecosystems, and its shallow spreading roots produce suckers that can make it difficult to control.

Key facts

Type: Weed, shrub.

Native to: Argentina, Brazil, Bolivia, Chile, Paraguay and Uruguay.

Established in: QLD, NSW, VIC, SA.

Other names: Green poisonberry, Chilean cestrum, Black nightshade, Willow leaved jessamine.

Best time to act: Find and remove plants before they flower and fruit; flowering occurs from spring to autumn.

Identification

  • A shrub growing up to 3 m high, often with several branches from the base and brittle, pale grey-brown branches.
  • Leaves are alternate, dark olive-green, lance-shaped or narrowly oval, usually 30–65 mm long, and foul-smelling when handled.
  • Pale yellow to greenish-yellow, narrow trumpet-shaped flowers grow in dense clusters at branch ends; they are sweetly scented at night and unpleasant-smelling during the day.
  • The fruit is a fleshy, deep purple to black, egg-shaped berry, 10–15 mm long, with several chunky seeds.
  • Shallow horizontal roots radiate from the plant and can produce suckers some distance away.
  • Look-alike: Lady of the Night (Cestrum nocturnum) has white berries and very slender flower tubes, only 1–3 mm wide; Green cestrum has purple-black berries and flower tubes 3–5 mm wide.

Where it grows

In Australia it is found across parts of NSW, Queensland, South Australia, Tasmania, Victoria and Western Australia, usually in moist, open disturbed places such as stream banks, roadsides, wasteland and urban bushland.

Why it matters

  • It is toxic to cattle, sheep, horses, pigs and poultry, which can die within hours after eating parts of the plant.
  • It is toxic to humans; its effect on native fauna is unknown.
  • It can invade native ecosystems, affect the structure and composition of coastal woodlands in Victoria, and out-compete vegetation on Queensland alluvial flats.
  • Dense stands can restrict access to waterways and prevent native plants establishing nearby.

How it spreads

  • Birds disperse the seeds.
  • Root segments can spread in soil carried by earth-moving equipment or in floodwater, including along riverbanks.
  • New infestations distant from existing occurrences have probably resulted from ornamental plants escaping from gardens.

Control options

  • Remove plants before flowering and fruiting, and before extensive horizontal roots form, to reduce spread by berries and suckering.
  • Remove all root material to help prevent regrowth; bulldozing may be effective and appropriate in some situations.
  • Monitor for regrowth and remove it mechanically or treat it with registered herbicides.
  • Seedlings may be suppressed by competition from other plants in suitable areas.

Hygiene and washdown

  • Clean earth-moving equipment and remove soil before moving between sites, as root segments can be transported in soil on machinery.
  • 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: Regional priority in 8 of 11 regions. Regional priority weed in Central Tablelands, Central West, Greater Sydney, Hunter, North Coast, North West, Northern Tablelands, Riverina. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Regionally prohibited / regionally controlled / restricted weed (varies by region). Where it is regionally prohibited, landowners must take all reasonable steps to eradicate it on their land. Where it is regionally controlled, landowners must take all reasonable steps to prevent its growth and spread on their land. Where it is a restricted weed, trade in it (including the plant, its seed or contaminated material) is prohibited.
  • 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: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • 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
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board

Sources