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Clockweed (Oenothera curtiflora)

Clockweed is an introduced weed of grain crops, disturbed sites and other environments in Australia. It can host powdery mildew that reduces crop yields, and it competes with native plants.

Key facts

Type: Weed, herb.

Native to: Central Mexico and central USA.

Established in: QLD, NSW, VIC.

Other names: butterfly plant, velvet weed.

Best time to act: Look for clockweed in summer when flowers are present, and treat actively growing plants before seed capsules mature.

Identification

  • An annual herb that grows upright to about 1 m tall, with soft hairs on its stems and a woody base.
  • Leaves form a basal rosette and grow alternately along the stems; they are oval, pointed, wavy-edged and have minute teeth.
  • Small white or light-pink flowers fade to red or pink and grow in spike-like clusters up to 40 cm long.
  • The flowers open for less than a day and are present in summer; dry, woody, ribbed capsules contain 3–4 seeds each.
  • The taproot can be up to 3 cm in diameter.

Where it grows

In NSW it is recorded mainly in the Riverina, with records from the North West to the Murray region, and grows on disturbed sites, in bushland, along waterways and in urban areas, parks and gardens.

Why it matters

  • It invades grain crops and can host powdery mildew, which may reduce crop yields.
  • It invades disturbed sites and competes with native plants.
  • It is drought tolerant and can grow in a range of cultivated and urban environments.

How it spreads

  • Plants may each produce up to 1,000 seeds.
  • Seeds may be spread by wind or when people dump garden waste.
  • The species has also been planted in gardens as an ornamental plant.

Control options

  • Hand-pull or hoe seedlings and small plants; removal is easier when the soil is damp.
  • For larger or dense infestations, use a suitable herbicide method such as spot spraying, a splatter gun or a weed wiper, following the current product label and any permit conditions.
  • Prevent plants from setting seed, and revisit treated areas to find and remove regrowth or new seedlings.
  • If found in the Western region, notify the local control authority; contact your local council weeds officer for identification advice.

Hygiene and washdown

  • Clean soil and plant material from boots, tools and machinery before leaving an infested site, and avoid moving material that may contain seeds.
  • Do not dump garden waste; dispose of removed plants and seed-bearing material 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: 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 1 of 11 regions. Regional priority weed in Western. 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: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • 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

Sources