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Willows (Salix spp.)

Willows (all except weeping willow, Salix babylonica, and a few sterile hybrids) invade streams and wetlands in south-eastern Australia, changing water flow and stream habitat.

Key facts

Type: Weed, tree.

Native to: Europe, Asia and the Americas.

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

Identification

  • Deciduous trees or shrubs with narrow, finely toothed leaves.
  • Flowers in catkins in spring.
  • Dense root mats along stream banks and in the channel.

Where it grows

Streams, rivers, wetlands and alpine bogs in cool temperate areas.

Why it matters

  • Choke stream channels and redirect flow, causing erosion and flooding.
  • Autumn leaf drop changes water quality.
  • Displace native riparian vegetation.

How it spreads

  • Broken twigs take root downstream.
  • Wind-blown seed from some species.

Control options

  • Stem injection or cut stump with registered herbicides suitable near water.
  • Staged removal with revegetation to protect the bank from erosion.

Hygiene and washdown

  • Do not leave cut stems in or near water, as they can strike.
  • 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): Weed of National Significance. One of 32 nationally agreed priority weeds, managed through national strategies with all states and territories.
  • Queensland: Restricted matter, category 3. Do not give it away, sell or release it into the environment. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Sale prohibited; Regional priority in 4 of 11 regions. It must not be imported into NSW or sold anywhere in the state. Regional priority weed in Greater Sydney, Murray, North Coast, Riverina. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Restricted weed. 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 (C1), some species prohibited. C1 Exclusion: to be kept out of WA, or out of the parts of WA where it is not established. Report any sighting to DPIRD. Some species must not be brought into WA (prohibited organism).
  • Tasmania: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • Australian Capital Territory: Declared pest, prohibited. It is a declared pest throughout the ACT. Dealing with it, such as selling, moving or keeping it, is prohibited.

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
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources