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Texas blueweed (Helianthus ciliaris)

In Australia, Texas blueweed is considered naturalised only in New South Wales, where it is widespread. It is highly competitive in several crops in the United States, but there is very little published information about its impacts on agriculture or the environment in Australia.

Key facts

Type: Weed, herb.

Native to: The United States of America and Mexico.

Established in: NSW.

Other names: Blueweed, Blueweed Sunflower, Yerba Parda.

Best time to act: In Australia, it flowers primarily in late spring and summer, and herbicides should be applied during its growing season.

Identification

  • This perennial herb grows 40–70 cm high and can form extensive colonies.
  • It has slender, creeping, rhizome-like roots, but no true rhizomes or thickened storage organs.
  • Its blue-green stems may trail or grow upright, and are hairless or have scattered stout hairs.
  • The narrow, blue-green leaves are mostly opposite, stalkless and generally hairless, with smooth or toothed margins.
  • Yellow petal-like florets surround reddish-purplish and yellow tubular florets.
  • Look-alike: Common sunflower is an erect annual or biennial with rough leaves covered in firm, stiff hairs; Texas blueweed has generally hairless leaves.
  • Look-alike: Jerusalem artichoke is a taller perennial with short rhizomes and tubers, and rough, hairy leaves; Texas blueweed lacks these features.

Where it grows

In Australia, it is considered naturalised only in New South Wales, where it occurs from north of the Victorian border in the South West Slopes to Coonabarabran in the North West Slopes; it has also been recorded once at Milford in Queensland.

Why it matters

  • In the United States, it is highly competitive in crops and cropping systems including cotton, wheat and sorghum.
  • There is virtually no published information about its impacts on agriculture or the environment in Australia.
  • At Milford, Queensland, it was recorded densely infesting four acres of a paddock in 1951, but there are no subsequent records from that area.

How it spreads

  • Vegetative spread by root fragments is its chief means of reproduction.
  • Machinery can drag root fragments from infested areas to clean sites, and disturbed infestations can spread through movement of contaminated soil or machinery.
  • It also reproduces by seed, but seed viability is often very low and can be less than 1%.

Control options

  • Registered herbicides are likely to provide the most effective control; apply them during the plant's growing season.
  • Small infestations and isolated plants can be hand-pulled, hoed or grubbed, with monitoring over several years to destroy resprouting plants.
  • Maintain a vigorous, competitive pasture and avoid overgrazing, which encourages the weed's growth.
  • Avoid mechanical disturbance of infestations because it can spread root fragments and worsen the problem.

Hygiene and washdown

  • Restrict movement of machinery, soil, agricultural seed, grain, forage and fodder from infested areas to clean areas, particularly where these may carry root fragments.
  • 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: 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.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development

Sources