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Onion weed (Asphodelus fistulosus)

Onion weed invades degraded pastures, rangelands and some native vegetation, and can compete strongly with cereal crops and other plants. It is unpalatable to livestock, reducing the carrying capacity of grazing land.

Key facts

Type: Weed, herb.

Native to: Mediterranean region through Asia Minor to western Asia and northern India.

Established in: NSW, VIC, TAS, SA, WA.

Other names: Asphodel, Hollow-stemmed Asphodel, Wild Onion.

Best time to act: Seeds germinate throughout the year, mainly in late summer and autumn, and plants generally flower from June to October.

Identification

  • An upright annual, biennial or short-lived perennial herb with a flowering stem up to 80 cm high.
  • Numerous hollow, round leaves grow from the base of the plant; they are often blue-green with a whitish bloom.
  • White or pink flowers grow along branched stems and have six petals, each with a brown or reddish stripe down the centre.
  • The flowers have orange anthers; the fruit is a wrinkled, almost globular capsule with brown or black seeds.
  • Look-alike: Strapweed or Dune Onion Weed (Trachyandra divaricata) has flat, sprawling leaves and a much-branched, wide-spreading flower head; Onion weed has hollow, upright leaves and a narrow, compact flower head.
  • Look-alike: Other plants called Onion Weed include Allium triquetrum, Nothoscordum borbonicum and Romulea rosea; Asphodelus fistulosus has cylindrical hollow stems and does not grow from bulbs or corms.

Where it grows

In Australia it occurs on roadsides, railway lines, neglected areas, poorer pastures and degraded or open native vegetation, including semi-arid areas and sandy coastal environments.

Why it matters

  • It competes strongly with other plants in degraded pastures and can compete with cereal crops.
  • Because livestock find it unpalatable, it can significantly reduce the carrying capacity of grazing land.
  • It invades degraded and open native vegetation and has also been recorded in relatively undisturbed open woodland.
  • It is thought to cause dermatitis in some people.

How it spreads

  • Onion weed reproduces by seed, dispersed mainly by wind when dead plants bearing seeds are blown about.
  • Seeds may also spread by water, vehicles, farm machinery, animals, wool, clothing and produce.

Control options

  • Preventing spread and targeting new infestations are the best management approaches; the plant does not usually invade well-managed pastures or cropping areas.
  • Hand-pulling is effective for outlying plants and small infestations; remove and bag flowering plants because they may continue to set seed after being pulled.
  • Cultivation can kill small plants in cropping areas, but large dislodged plants can re-root and may block pronged implements.
  • Registered herbicides are available, although broad-scale herbicide use is expensive.

Hygiene and washdown

  • Seeds can spread on vehicles, farm machinery, animals, wool, clothing and produce, so clean potentially contaminated equipment and clothing before moving between sites.
  • Check vehicles and machinery for plant material and seeds after working in infested areas.
  • 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: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • 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.

  • 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
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • 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

Sources