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Bitterweed (Helenium amarum)

Helenium amarum is an introduced annual recorded in Queensland, where it is considered an environmental weed and has been subject to control and surveillance. It can quickly colonise open, disturbed ground, and its toxicity can harm livestock and make milk and eggs bitter.

Key facts

Type: Weed, herb.

Native to: Northern Mexico and parts of the United States.

Established in: QLD.

Other names: Bitter sneezeweed, Yellow sneezeweed, Fiveleaf sneezeweed, Spanish daisy.

Best time to act: Look for and treat plants before they set seed, with inspections timed for their flowering period in Australia, which occurs in late spring or summer.

Identification

  • An annual herb that grows about 10 to 100 cm tall, with stems that are usually branched near the top.
  • Leaves are generally narrow and linear, with some lower leaves broader or toothed.
  • It bears daisy-like heads with yellow ray florets; the central florets can be yellow, yellow-brown or purple toward their tips.
  • Some plants have flowers with a red-brown centre, and the small fruits are hairy.
  • Look-alike: Helenium autumnale has similar-looking flowers, but its stems have green wings and its flowers have wedge-shaped, bright yellow rays.

Where it grows

In Queensland it grows in open, disturbed places such as roadsides, pastures, wasteland and other areas of bare ground.

Why it matters

  • All parts of the plant contain the toxic glycoside gudaldin; animals that eat it can develop weakness, diarrhoea and vomiting, and large quantities can be fatal to livestock.
  • Even small amounts eaten by grazing animals can make cows' milk and chickens' eggs bitter and unsuitable for human consumption.
  • It can spread quickly where taller vegetation has been removed and may become abundant in open fields, roadsides and wasteland.
  • It is considered an environmental weed in Queensland and has been subject to control efforts.

How it spreads

  • It spreads by seed, which may be dispersed by animals and wind.
  • Seeds or plants may be moved accidentally with aircraft, soil, gravel or vehicles.
  • It is also grown as an ornamental, and seeds are sold online, creating potential pathways for deliberate introduction.

Control options

  • Hand-pull or dig out plants while they are small and before they set seed, taking care to contain any seed-bearing material.
  • Bag and dispose of seeding plants as directed by local authorities; do not leave seed-bearing material where it can spread.
  • For larger infestations, use only herbicides currently registered for the target and site, and follow the product label and local biosecurity advice.
  • Reinspect treated areas regularly, remove new seedlings or survivors, and report suspected occurrences to the relevant state or territory biosecurity agency where appropriate.

Hygiene and washdown

  • Before leaving an infested site, clean seeds and soil from vehicles, machinery, boots and tools, and contain and dispose of the debris so it cannot spread.
  • 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: Restricted matter, categories 2, 3, 4, 5. Report it to Biosecurity Queensland within 24 hours; do not give it away, sell or release it into the environment; do not move it; do not keep it. 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 (C1), prohibited. C1 Exclusion: to be kept out of WA, or out of the parts of WA where it is not established. Report any sighting to DPIRD. It must not be brought into WA (prohibited organism).
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • 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)

Sources