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Skeleton weed (Chondrilla juncea)

Skeleton weed is a serious weed of cultivation, particularly in Australian wheat-growing areas, where it competes with crops and can reduce yields by up to 80%. Its deep, extensive roots and ability to regrow from root fragments make it difficult to eradicate, while tangled stems can disrupt harvesting.

Key facts

Type: Weed, herb.

Native to: Western Europe, the Mediterranean region and north Africa to central Asia.

Established in: QLD, NSW, ACT, VIC, SA, WA.

Other names: Rush Skeleton Weed, Rush Skeletonweed, Naked Weed, Gum Succory.

Best time to act: Look for rosettes after autumn rains and through winter, and control plants before seeds form; hand-pull small infestations when the soil is wet.

Identification

  • It grows as a biennial or perennial herb, up to 1.3 metres high, with a deep taproot and branching lateral roots.
  • Young plants form a low rosette of lobed or toothed leaves; these leaves usually wither as the plant flowers.
  • Flowering plants have upright, wiry, much-branched green stems that are almost leafless and exude milky latex when cut or broken.
  • Numerous small yellow daisy-like flower heads appear along the upper stems from late spring to autumn.
  • Its narrow, ribbed fruits have a conspicuous beak and a white, parachute-like tuft of hairs.
  • Look-alike: In the rosette stage it can resemble Cat's-ears, hawksbeards, Hairy Hawkbit, dandelions, Willow Leaf Lettuce, Prickly Lettuce and Capeweed; flowering Skeleton Weed has wiry, almost leafless stems and milky latex.
  • Look-alike: Chicory has purplish-blue or rarely white flowers, while Rough Sowthistle has numerous stem leaves with spiny, wavy margins.

Where it grows

In Australia it occurs across much of south-eastern Australia and south-western Western Australia, in wheat-growing areas, pastures, orchards, gardens, roadsides and other disturbed sites, as well as some native vegetation.

Why it matters

  • It competes strongly with crops for moisture and nutrients, especially nitrogen, and can substantially reduce cereal yields.
  • Tangled, tough stems can choke harvesting machinery, cause wear and breakdowns, and make harvesting difficult.
  • It can compete with fodder plants in pastures; after the rosette leaves die, infested areas may yield little fodder in autumn and winter.
  • It can invade native vegetation, generally where areas have been affected by drought or overgrazing.

How it spreads

  • A single plant can produce 27,000 seeds per year; seeds are dispersed by wind and can attach to wool, fur, clothing and other materials.
  • Cultivation and farm machinery can spread root pieces and underground stems, which may regrow into new plants when moisture is available.
  • Seeds may be moved in contaminated wool, grain, hay or chaff, and on machinery, vehicles, railway trucks and boots.

Control options

  • Avoid cultivating infested areas because cut roots and underground stems can regrow and spread; prevent plants from setting seed.
  • Use registered herbicides as part of an integrated program; deep roots make control difficult and multiple applications may be needed.
  • Mow pastures before seeds form, and hand-pull small infestations when the soil is wet, repeating over several years because roots may resprout.
  • Use competitive crops or strong pastures and grazing to suppress plants and reduce seed production, and regularly monitor infested and treated areas.

Hygiene and washdown

  • Check and clean farm equipment, vehicles, boots and other items to remove seeds and root pieces before moving them from infested areas.
  • Avoid moving contaminated wool, grain, hay or chaff into uninfested 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: 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: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • Western Australia: Declared pest (C2, C3). C2 Eradication: present in limited areas and targeted for eradication. C3 Management: landholders must manage it to reduce its impact and stop it spreading.
  • Tasmania: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • 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
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • 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
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources