Quick Facts

Quick facts

  • Salix spp. except S.babylonica, S.x calodendron & S.x reichardtii
  • Willows are invasive weeds of many waterways and wetlands in south-eastern Australia.
  • Willows spread their roots into the bed of a watercourse, slowing the flow of water and reducing aeration.
  • Willows are easily killed with herbicide but difficult to control because broken stems and twigs easily take root.
  • Some varieties of Willow can also spread by seed, which can be carried up to 100 km by wind or water.
  • Willows have started to invade natural habitats.

What Does It Look Like?

What is it?

Worldwide, there are over 330 accepted willow (Salix) species with over 170 accepted hybrids. Willows are commonly trees or shrubs, rarely herbaceous (herbs) (POWO 2020), are  mostly dioecious (having male and female plants with  separate male and female flowers on different plants) rarely monoecious (having separate male and female flowers on the same plant) VicFlora (2016). In Australia  approximately 100 different taxa (species, varieties, cultivars and hybrids)  have been introduced (Clift and Davies 2007) with 25 taxa recorded as weeds (APC 2020). In Australia they are all deciduous trees or shrubs, most or all with four distinctive growth habits recognisable among the group: the pencil willows, the tree willows, the weeping willows and the shrub willows.

The pencil willows have a single trunk capable of growing into a large tree, with very short lateral branches forming a narrow crown, where the branches get progressively shorter from the base of the trunk to the apex.

The tree willows have a single or several trunks, capable of growing into large spreading trees, with upright large branches.

The weeping willows are within the tree willows is another group that have branches that hang down and this group is known as .

The shrub willows are multi-stemmed and never grow into trees.

All willows form large dense shallow root masses. The leaves of most species are long and narrow with fine toothed margins. Salix cinerea (Grey Sallow or Pussy Willow) has broader, shorter leaves than the rest.

The flowers of willows are uni-sexual (exclusively male or female) and group together in what is called a catkin, with male catkins and female catkins usually formed on separate plants (dioecious).

The small seeds develop quickly inside a capsule. Each seed has long silky hairs at one end which aids in the wind dispersal of the seed once the capsule opens. The seeds are short lived and normally don't live longer than 10 days.

Most naturalised Willow populations are hyrbids and can be practically impossible to identify precisely (CRC 2003). Useful identification sources can also be found in the Willows Resource Kit (available through Agriculture Victoria, at: http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/weeds_trees_willow_resource_sheet/$FILE/Resource%20Sheet%202%20-%20Willow%20Identification.pdf ) and the Willows Management guide (available through the Western Australian Government site, at: https://library.dbca.wa.gov.au/static/FullTextFiles/629078.pdf), and Willows Best Management guide (available at: http://www.sgln.net.au/wp-content/uploads/2017/03/salix.pdf)

For further information and assistance with identification of willows contact the herbarium in your state or territory.

Flower colour


Growth form (weed type/habit)

Tree or shrub

Where it currently grows? Preferred habitat

Willows occur naturally in permanently or seasonally wet, inundated or waterlogged sites (CRC 2003). In Australia they are mainly found in similar situations along water courses or in seasonal or permanently wet areas.

Are there similar species?

The Willows may be confused with the Poplars (Populus spp.), another introduced group which has been planted widely in Australia and has also become weedy in parts. Poplars normally have broader, glossy leaves and longer, dangling catkins. They are more often found planted away from rivers. Willows are unlikely to be confused with any Australian native species.

Why Is It A Weed?

What are its impacts?

Most species of Willow are Weeds of National Significance. They are among the worst weeds in Australia because of their invasiveness, potential for spread, and economic and environmental impacts. They have invaded riverbanks and wetlands in temperate Australia, occupying thousands of kilometres of streams and numerous wetland areas (CRC 2003).

Agriculture: Willow thickets can restrict access to waterway impacting livestock.

Water use: The amount of water willows use when located in the stream bed is substantially higher than native trees, which is damaging for water availability and water quality (CRC 2003). Field research in the Murray-Darling Basin has indicated that in cool temperate climates an average net water saving of 3.9ML a year could be achieved for each hectare of willow canopy removed, and in semi-arid climates this could be as high as an average of 5.5 ML (Doody and Benyon 2011).

Native ecosystems: Willows spread their roots into the bed of a watercourse, slowing the flow of water and reducing aeration. Willows form thickets which divert water outside the main watercourse or channel, causing flooding, instability and erosion where the creek banks are vulnerable, as they can grow into water courses, changing ecosystems. As Willows are winter deciduous (all leaves fall from the tree for winter), the leaves fall into in water courses. This creates a flush of organic matter reducing water quality and available oxygen, directly threatening aquatic plants and animals. The replacement of native vegetation (e.g. river red gums) by willows reduces habitat (e.g. nesting hollows, snags) for both land and aquatic animals (CRC 2003). Willows have only invaded about 5% of their potential geographic range in temperate Australia (CRC 2003).

Urban areas: Willows form dense impenetrable thickets and reduce or eliminate visual and physical access to water bodies. Willows form dense root mats and produce dense stems that block access for boats, canoes and rafts used for fishing and other aquatic activities. The spreading nature of Willows on waterways can also damage infrastructure.

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. Fishermen often break off twigs and stick them in the riverbank to hold their lines, and these pieces will also grow (CRC 2003).

Seed is the main method of spread for several species, especially Grey Sallow and Black Willow. These species can invade off-stream wetlands from sea level to alpine locations. Seed carried by wind or water easily travels more than 1 km, with small amounts potentially spreading up to 100 km (CRC 2003).

Willows can also reproduce prolifically from seed, producing seedlings resulting from cross-pollination between different types. Hybrids, resulting from interbreeding between different hybrids or cultivars, are still being identified in the north-east of Victoria. Willows can germinate in massive numbers (half a million seedlings were recorded at one site), and form islands in watercourses (Albury/Wodonga Willow Management Working Group 1998).

However, often these seeds do not germinate or grow, possibly due to the lack of suitable seedbed, rising or rapidly falling water levels and floods that uproot or bury the seedlings (National Willows Program Resource Kit undated).

What is its history in Australia?

Willows have been used for soil stabilisation and river bank protection, basketry, landscaping, shade and shelter. Tortured Willows (Salix matsudana hybrids) from New Zealand were introduced into the Murray-Darling Basin during the 1980s and have only recently begun to cause problems (CRC 2003).

The Cricket-bat Willow (Salix alba var. caerulea) is cultivated in parts of Australia but has not naturalised (Carr 1996).

How To Manage It?

Best practice management

Early detection and control are essential to prevent the spread of new infestations. The deliberate planting of willows along waterways has virtually ceased and extensive removal operations are common. Willows are relatively easy to kill and mechanical and chemical control techniques are well understood. However, it should be noted that indiscriminate removal of willows is not recommended as it may lead to stream instability. Control should be conducted in consultation with state or territory authorities (CRC 2003). See Holland and Davies (2007) for managing Willows and the variety of control options available.

Chemical control: Herbicides available for woody weeds are effective in controlling Willow. Trees can be killed by stem injection, application to leaves and stems, bark (chemical girdling) and cut and paint methods (check with state/territory agencies for current recommendations). In dry conditions herbicide can also be applied by basal bark spraying and treatment of seedlings. Although stem injection may be a slower, more laborious method, it is an important option for avoiding chemical runoff and protecting native vegetation. In general, herbicide should be applied from summer to early autumn, although stem injection or cut and paint application is effective year round (CRC 2003). Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au.

NOTE: Training is normally a requirement in most States and Territories for all or some of the methods.

Non-chemical control: Physical control: The value of physical controls (hand-pulling  or manual) is limited to small and isolated situations and could be particularly useful in removing initial invaders of a catchment if they can be located early enough. Elimination of young seedlings is a cost effective way of keeping waterways free of potential blockages, erosion and stream bed change. 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 (CRC 2003). Mechanical control: Using large machinery such as excavators or bulldozers to remove larger trees and root systems is not recommended except in dry areas. In wet areas bulldozers push broken branches into the ground and thus generate numerous new plants (CRC 2003).

Disposal: Trees killed while they are standing (i.e. by stem injection) should be left for 12 months before they are removed. They can then be cut at a suitable height and stacked away from watercourses. If it is necessary to remove live trunks and limbs from the site, stack them to dry above flood level, taking care to minimise the spread of small pieces. Smaller twigs should be bagged and disposed of at tip facilities so that they do not sprout and cause further problems (CRC 2003).

Biological control: Willow Sawfly (Nematus oligospilus) had accidentally arrived in Australia and was first reported in Canberra in 2004 and by April 2006 it had arrived in the ACT, NSW, South Australia, Victoria and Tasmania. Larvae of this insect feed on Willow leaves and large populations of sawfly larvae can defoliate Willow trees. However, Willow Sawfly has not had a great impact on control of Willows. 


Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

In Australia, Willows normally flower around September or October with flowers only lasting 2 to 3 weeks. Fruit develops quickly and seed is normally shed around November. The seed is short lived and normally doesn't live much longer than 10 days (Cremer 1995; CRC 2003). Germination is very fast, occurring within 24 hours, and seedlings grow rapidly under favourable conditions (CRC 2003).

Willows are either male or female and most groups in Australia are single-sex clones. However, they readily hybridise when opposite sexes come together. The hybrid species are vigorous and can breed just two or three years after germination (CRC 2003).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

Willows are confined to the south-west corner of Western Australia and the south-east regions of Australia from south-east Queensland through the Northern, Central and Southern Tablelands and some coastal regions of New South Wales. They are widespread in eastern and central Victoria and found in south-eastern South Australia, particularly along the Murray River and some of its tributaries. Willows are also widespread in Tasmania.

Where does it originate?

All willows in Australia have been introduced from other countries, with most probably coming from Europe. Most species presently growing in Australia are found naturally in Great Britain and Ireland (Meikle 1984).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?

Declared in all Australian states and Territories.

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Salix spp. except Salix babylonica, Salix x calodendron & Salix x reichardtii

Other scientific names (synonyms)?


Does it have other known common name(s)?

Basket Willow (Salix viminalis L.), Basket Willow (Salix x rubens Schrank), Black Willow (Salix nigra Marshall), Broadleaf Willow (Salix myricoidesMuhl.), Common Osier (Salix viminalis L.), Common Sallow (Salix cinerea L. var. cinerea), Crack Willow (Salix fragilis L. var. fragilis), Cricket-bat Willow (Salix alba var. caerulea (Sm.) Sm.), Forked-catkin Crack Willow (Salix fragilis var. furcata Gaudin), Gold-crack Willow (Salix x rubens Schrank), Golden upright Willow (Salix alba var. vitellina (L.) Stokes), Golden Weeping Willow (Salix x sepulcralis var. chrysocoma (Dode) Meikle), Golden Willow (Salix alba var. vitellina (L.) Stokes), Grey Sallow (Salix cinerea L. var. cinerea), Pencil Willow (Salix humboldtiana 'Pyramidalis'), Purple Osier (Salix purpurea L.), Pussy Willow (Salix cinerea L. var. cinerea), Rusty Sallow (Salix cinerea var. oleifolia (Sm.) Macreight), Tortured Willow (Salix matsudana Koidz.), Weeping Willow (Salix x pendulina Wender), Weeping Willow (Salix x sepulcralis Simonk.), White Willow (Salix alba L. var. alba) 

National Weed Management Guide

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