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Great mullein (Verbascum thapsus)

Great mullein is generally not grazed and can replace pasture, potentially reducing carrying capacity. It can also invade open, undisturbed ecosystems and displace native herbs and grasses.

Key facts

Type: Weed, herb.

Native to: Western and central Asia and Europe.

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

Other names: Shepherd's Blanket, Aaron's Rod, Woolly Mullein, Blanket Weed.

Best time to act: Look for rosettes and treat them before flowering, with herbicide treatment timed for active growth in autumn, winter or spring.

Identification

  • This annual or biennial herb grows 1–3 m tall and has a deep, stout taproot.
  • It first forms a large basal rosette of grey-green leaves, which are densely covered with soft, star-shaped hairs.
  • Mature plants usually have a single robust, upright flowering stem, with leaves becoming smaller towards the top.
  • Pale yellow to yellow flowers are densely clustered along a long spike-like stem; the rounded or egg-shaped capsules contain tiny reddish-brown seeds.
  • Look-alike: Twiggy mullein (Verbascum virgatum) has darker, more sparsely hairy leaves, coarsely toothed margins and often branched, less robust flowering stems; its flowers are more widely spaced.
  • Look-alike: Moth mullein (Verbascum blattaria) has darker green, hairless or sparsely hairy leaves that are deeply toothed or lobed, and flowers on longer stalks.

Where it grows

In Australia it occurs in all states except the Northern Territory, mainly in temperate regions, including pastures, roadsides, waste areas, creek beds and forest margins.

Why it matters

  • It is generally not grazed, and can replace pasture and potentially reduce carrying capacity.
  • It can displace native herbs and grasses in open ecosystems, and dense populations may significantly alter plant community structure.

How it spreads

  • Great mullein spreads by seed only and can produce an estimated 100,000 to 240,000 seeds per plant; seeds may remain viable for up to 100 years.
  • The tiny seeds can contaminate soil or agricultural produce and can be dispersed by wind, water or animals.
  • Most seeds fall close to the parent plant.

Control options

  • Pull or grub plants, especially seedlings, removing as much of the taproot as possible and treating before flowering.
  • If flowering has occurred, remove, bag and dispose of all flowering structures, taking care to remove and destroy fruits and seeds.
  • Avoid unnecessary soil disturbance when pulling, as loosening the soil can stimulate seed germination; larger patches may be cultivated, followed by checks for seedlings in later seasons.
  • Registered herbicides can be useful when applied to leaves at the rosette stage before flowering, while plants are actively growing in autumn, winter or spring.

Hygiene and washdown

  • Tiny seeds can contaminate soil and agricultural produce, so check soil and produce from infested sites before moving them.
  • 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 controlled / restricted weed (varies by region). 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: 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.

  • 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
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board

Sources