Grey sallow (Salix cinerea)

Also known as: pussy willow, grey willow, common sallow, wild pussy willow

Grey sallow is a deciduous, spreading shrub or tree. It is a type of willow that invades the banks of waterways reducing water quality and causing flooding, bank instability and erosion.

Profile

How does this weed affect you?

Grey sallows form dense stands along the banks of waterways and their roots spread into the bed of waterways. They:

• outcompete native plants
• reduce food and habitat for land and aquatic animals
• reduce water quality (especially when they drop their leaves in autumn)
• take up large amounts of water
• change water flows
• divert flood waters and cause erosion
• restrict access to waterways.

What does it look like?

Grey sallow is a type of willow which can be a deciduous shrub or tree. The shrub form is 1–2 m tall and is wider than it is high. The canopy has a characteristic dome shape. The tree form is up to 12 m tall.

Leaves are:

• dark green on top
• blue-green underneath
• 2–9 cm long and 1–4 cm wide
• oval-shaped with a short, pointed tip
• hairy on both sides when young
• only hairy underneath when older.

Flowers:

Male and female flowers are usually on separate plants but occasionally both are on the same plant. All flowers are present in spring.

Male flowers are:

• yellow with no petals
• fragrant
• in clusters (catkins) 1.5–3.5 cm long and 1–2 cm wide.

Female flowers are:

• green with no petals
• soft and fluffy
• grouped densely in cylindrical clusters 1.2–3 cm long initially then elongating up to 11 cm long and 1.3–1.8 cm wide.

Fruit:

• are a capsule that splits into two sections
• are up to 1 cm long
• contain seeds with long silky hairs.

Stems are:

• numerous from 5 to more than 50
• upright when young and slightly drooping when mature
• hairy when young, becoming hairless with age
• dark reddish-brown when young
• flexible at the base and hard to break
• with long visible ridges when the bark is removed.

Bark is:

• dark grey to dark grey-brown in colour
• smooth when young
• grooved when mature.

Similar looking plants

Grey sallow looks similar to Black willow (Salix nigra), which is a taller tree up to 20 m and has a single trunk or up to 4 stems from the base. The leaves are longer, thinner, have toothed edges and are hairless.

Where is it found?

Grey sallow grows in the tableland regions of NSW and the Greater Sydney region.

It is native to Eurasia and northern Africa. Grey sallow has become a weed in New Zealand and the USA. It was originally planted, along with other willow species, for erosion control, stream bank stabilisation and windbreaks.

What type of environment does it grow in?

Grey sallow prefers cool temperate climates. It can invade both disturbed and undisturbed areas. It will grow at various altitudes as long as the location is sunny and is seasonally waterlogged. It tolerates frost and a wide range of soils including neutral and acidic soils.

It is the only willow species that grows outside waterways. With enough soil moisture, it can form dense stands in a variety of environments including:

• rivers and streams
• wetland
• swamps
• wet forests
• boggy alpine areas
• drains.

Maps and records

• Recorded presence of Grey sallow during property inspections (Map: Biosecurity Information System - Weeds, 2017-2023)
  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?

By seed

Most spread is via seeds. Plants produce thousands of seeds each year but seeds are only viable for 8 weeks at the most.

Grey sallow infestations, with relatively few plants causing little impact, can remain stable in size for a long period of time. However, when ideal conditions occur, with bare moist ground and sunlight, masses of seedlings can quickly germinate. This causes a rapid and large increase in the number of grey sallow plants.

Grey sallow can cross-pollinate with other willow species forming hybrids. Hybrids can potentially be more invasive than the parent trees.

Wind and water spread the light, fluffy seeds. Seeds can spread up to 100 km via water.

By plant parts

Grey sallow can grow from small pieces of plants. Branches and twigs break off and travel many kilometres downstream. When they stop moving, they develop roots resulting in new infestations.

References

CABI invasive species compendium online data sheet. Salix cinerea. CABI Publishing 2011. www.cabi.org/ISC. Accessed August 2014.

Holland C. S. (2008) National willows resource kit, resource sheet 2: willow identification, an essential skill for effective willow management, Victorian Department of Primary Industries, Geelong.

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

Hopley, T. & Young, A. G. (2015). Knowledge of the reproductive ecology of the invasive Salix cinerea, in its invaded range, assists in more targeted management strategies. Australian Journal of Botany, 63(6), 477-483.

Muyt, A. (2001). Bush invaders of South-East Australia: a guide to the identification and control of environmental weeds found in South-East Australia. RG and FJ Richardson.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 28 June 2021 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Salix~nigra

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

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 and 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 grey sallow:

• work on upstream infestations first
• remove trees on inside bends of rivers first as these have more stable banks
• control plants before they produce fruit
• 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 small seedlings up to 0.5 m tall. Small roots left in the ground do not usually regrow.

By machine

Only use 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.

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

Only spray willows less than 2 m tall. 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. Cover all of the foliage with herbicide. Only spray plants with clean foliage. Silt on the leaves can reduce herbicide uptake.    

Stem injection

When: Year round but best results are in summer and early autumn.

Follow up: Wait at least 12 months after treatment.

Stem injection is suited to large trees. Make cuts or drill holes low all around the trunk to penetrate the spawood 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

When: Year round.

Follow up: Check and control regrowth or new seedlings in spring-summer.

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 to 1.3 L in 100 L of water
Comments: Use higher rate for trees 1 to 2 m tall
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 application: Apply a 3–5 mm layer of gel for stems less than 20 mm. Apply 5 mm layer on stems above 20 mm. Stem inject application for trees: Make a series of cuts 15-20 mm deep around the trunk using an axe or saw. Space cuts evenly with no more than a 20-40 mm gap between them. 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 L in 15 L of diesel
Comments: Cut stump application for stems greater than 10 cm. 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 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.
Greater Sydney	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
Murray	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
North Coast	Regional Recommended Measure* (for Regional Priority - Eradication) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
Riverina Core infestation areas: Snowy Valleys Council, Cootamundra - Gundagai Regional Council, Wagga Wagga City Council. Exclusion zone: All of Riverina except identified core infestation areas.	Regional Recommended Measure* (for Regional Priority - Containment) Within exclusion zone: Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. Within core infestation area: Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
	*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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Reviewed 2023