Willows (Salix species)

Willows are deciduous trees or shrubs that form large, dense root-mats on the surface of the soil or in shallow water and slow-moving streams. They invade thousands of kilometres of riverbanks and numerous wetlands in temperate Australia.

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How does this weed affect you?

Willows:

• compete with native plants
• reduce habitat and food for native animals, both land and aquatic
• reduce water quality and oxygen levels when they drop all of their leaves in autumn
• form thickets which divert water, causing flooding and erosion where the creek banks are vulnerable
• use large amounts of water, drying small streams and swamps
• reduce access for boating and other recreational activities
• damage infrastructure when floating trunks are washed downstream.

What does it look like?

Willows are deciduous trees or shrubs. They have small seeds with long, silky hairs attached to one end like a parachute, which help them spread. The seeds are usually short-lived, from days to a few weeks. With the exception of the pussy willows, the leaves of all species are long and narrow, with finely toothed edges and usually a paler underside. Upright catkins (flower stalks) carry numerous tiny flowers. The trees form large, dense root-mats on the surface of the soil or in shallow water and slow-moving streams.

Where is it found?

 Willows have only invaded about 5% of their potential geographic range in temperate Australia. The most seriously invasive willow, grey sallow (Salix cinerea), is expanding its range rapidly in Victoria and New South Wales, and possibly in Tasmania.

Grey sallow or pussy willow (Salix cinerea) is the most seriously invasive willow in Australia. It is a large spreading shrub or small tree with twigs or branches that are hard to break. It reproduces mainly by seed. Pussy willow is highly invasive in swamps, drainage lines and other moist sites including lowland and mountain streams. Large and rapidly expanding populations occur in Victoria, and this species will probably become a major wetland and riverside weed (as it is in New Zealand). It forms hybrids with other shrub willows.

Crack willow (Salix fragilis var. fragilis) and basket willow (Salix x rubens) are by far the most widespread and abundant willows in Australia, and are the most serious problem willow in Tasmania. They are found along thousands of kilometres of streams in southeastern Australia where they were widely planted for stream stabilisation. Crack willow spreads almost exclusively by plant parts so it is only associated with streams.

Black willow (Salix nigra) has been widely planted in northeastern Victoria and at several sites in New South Wales. It is now very abundant in some streams. Black willow has the potential to behave in the same invasive manner as grey sallow in wetlands.

Maps and records

• Recorded presence of Willows during property inspections (Map: Biosecurity Information System - Weeds, 2017-2026)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

Most willows spread by fragments of stems or twigs breaking off and growing new roots in water. Pieces can travel many kilometres before establishing at a new site. 

Seed is the main method of spread for several species, especially grey sallow and black willow. Seed carried by wind or water easily travels more than 1 km, with small amounts potentially spreading up to 100 km. Seed production is becoming more common as more willows are introduced into Australia. However, the conditions required for germination (ie continuously wet, bare sediment) do not commonly occur and the seed only remains viable for between two and six weeks, depending on the species.

Willows are either male or female and most groups in Australia are single-sex clones. However, they readily hybridise when opposite sexes come together. They flower in spring, the flowers only lasting for 2–3 weeks. The tiny seeds ripen about 3–4 weeks later in late spring or early summer. Germination is very fast, occurring within 24 hours, and seedlings grow rapidly under favourable conditions. The hybrid species are vigorous and can breed just two or three years after germination.

There are 32 different groups (species, varieties, subspecies and hybrids) of willows in Australia. Nearly all the different species have become naturalised here and can cross-breed with other willow species that flower at the same time. Most naturalised willow populations are hybrids and can be practically impossible to identify precisely.

The introduction of New Zealand willows (Salix matsudana hybrids) throughout the Murray–Darling Basin in the 1980s and their widespread sale since then is now causing problems, as the females produce abundant seed and the males fertilise the weeping willow (Salix babylonica), a widespread species that in the past usually did not seed because it had no male partner flowering at the same time.

What type of environment does it grow in?

Willows occur naturally in permanently or seasonally wet, inundated or waterlogged sites. The largest infestations in Australia are in Victoria, Tasmania, New South Wales and the Australian Capital Territory. Several species (weeping, basket and crack willows) have been widely planted along the rural waterways of southeastern Australia for erosion control.

Acknowledgements

Information and guide revision: Bob Trounce (NSW Agriculture), Lynton Auld (Blue Mountains City Council), Richard Carter (NSW Agriculture/Weeds CRC), Vanessa Richardson (NSW NPWS) and John Thorp (National Weeds Management Facilitator). 

This information was generated by the CRC for Australian Weed Management. 

References

Holland, C.S. & Davies, J. (2007) Willows National Management Guide: current management and cotnrol options for Willows. (Salix spp.) in Australia. Victorian Department of Primary Industries. Gelong Vic.

Weeds of National Significance (2003) Weed Management Guide Willow - Salix spp. 

More information

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Control

Successful weed control requires follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful.

Clearing any vegetation along waterways may cause erosion or stream instability. Clearing may require consent before any work starts. It is the landholder’s responsibility to obtain any approvals that may be required prior to undertaking clearing. NSW Local Land Services staff can assist you in understanding what other approvals may be required for your proposed activities under the Land Management Framework. Contact NSW Local Land Services for advice on the required approvals for your site.

 To manage willows:

• work on upstream infestations first
• remove trees on inside bends of rivers first as these have more stable banks
• control plants before they produce seeds
• use appropriate methods of control for the size of the plants
• dispose of all plant parts away from flood zones
• look for and control new seedlings
• look for and control regrowth for 3–5 years.

Physical removal

By hand

Dig out or hand pull rooted branches and small seedlings up to 0.5 m tall. Small roots left in the ground do not usually regrow.

By machine

Only use large machinery such as excavators or bulldozers to remove larger trees and root systems in dry areas. In wet areas machinery pushes broken branches into the ground which produces many new plants. .  Hand pulling of seedlings less than 0.5 m tall is the most practical and environmentally safe way of removing young plants. Leaving small roots in the ground does not lead to suckering or regrowth. 

Disposal

Trees killed by stem injection should be left for 12 months before they are cut and removed. Plants should not be chipped unless they have been treated with herbicide. Removed plant parts should be stored away from flood prone areas. Small plant parts such as twigs can be bagged and disposed of at some waste centres. Contact your local council for advice on how to dispose of willows.

Chemical control

Spraying

Spray willows less than 2 m tall. Cover all of the foliage with herbicide. Only spray plants with clean foliage because silt on the leaves can reduce herbicide uptake. Do not spray in autumn if the leaves have started to fall. Spray in areas where herbicides will not affect native plants or water bodies.

Stem injection

Stem injection is suited to large trees. Make cuts or drill holes low all around the trunk to penetrate the sapwood below the bark. Inject herbicide within 15 seconds into each cut or hole. Leave the tree undisturbed for at least 12 months after treatment. After 12 months the trunks can be cut and stacked away from water flows. The tree may regrow if the timber is cut too soon.

Cut stump method

Cut the trunk off below the first branches and immediately apply herbicide to both the trunk and the cut stump. Only use this method when all the cut material can be safely disposed of.

Herbicide options

See Using herbicides for more information.

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Glyphosate 360 g/L (Various products)
Rate: 1.0–1.3 L in 100 L of water
Comments: Spray to wet all foliage. Use the higher rate for trees 1–2 m high. If trees are in riparian zones, use herbicide registered for aquatic use.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: Undiluted
Comments: Stem injection. For trees with a basal diameter of 0 - 25 cm use 1 mL/cut. For trees with a basal diameter of 25 - 60 cm use 2 mL /cut.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Picloram 44.7 g/L + Aminopyralid 4.47 g/L (Vigilant II ®)
Rate: Undiluted
Comments: Cut stump for small plants: Apply a 3–5 mm layer of gel onto stems less than 2 cm diameter. Apply 5 mm layer on stems above 2 cm diameter. Stem inject trees: Make evenly spaced cuts 1.5-2 cm deep around the trunk. Apply a 5 mm layer of gel over the lower surface of the cut.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Triclopyr 240 g/L + Picloram 120 g/L (Access™ )
Rate: 1.0 L in 15 L of diesel
Comments: Cut stump application for plants with a basal stem greater than 10 cm in diameter. Need to treat all stems.
Withholding period: Nil
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the NSW Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW	Prohibition on certain dealings Must not be imported into the state, sold, bartered, exchanged or offered for sale. All species in the Salix genus have this requirement, except Salix babylonica (weeping willows ), Salix x calodendron (pussy willow) and Salix x reichardtii (sterile pussy willow)

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Reviewed 2025