Weeds of Australia - Fact Sheet

Top Scientific Name Synonyms Family Common Names Origin Cultivation Naturalised Distribution Habitat Habit Distinguishing Features Stems and Leaves Flowers and Fruit Reproduction and Dispersal Environmental Impact Legislation Management Similar Species

Scientific Name

Salix fragilis L.

Synonyms

Salix fragilis L. var. fragilis
Salix fragilis L. var. furcata Gaudin

Family

Salicaceae

Common Names

basket willow, brittle willow, crack willow, fragile willow

Origin

This species is thought to be native to most southern and central Europe (i.e. France, Spain, Austria, Belgium, Czechoslovakia, Germany, Hungary, the Netherlands, Poland, Switzerland, Albania, Bulgaria, Greece, Italy, Romania, Yugoslavia, Belarus, Estonia, Latvia, Lithuania, Moldova, Ukraine and western Russia) and western Asia (i.e. Turkey). However, its exact native is uncertain due to confusion with Salix x rubens.

Cultivation

Crack willow (Salix fragilis) has been widely planted around waterbodies and along waterways in the temperate regions of Australia, mainly to prevent soil erosion.

Naturalised Distribution

Widely naturalised in south-eastern Australia (i.e. in eastern New South Wales, the ACT, Victoria and Tasmania).

Also naturalised overseas in southern Africa, New Zealand, and North America (i.e. the USA and Canada).

Habitat

A weed of waterways, riparian vegetation, lake edges, billabongs, swamps and wetlands in wetter temperate regions.

Habit

An upright (i.e. erect) and spreading tree that loses it leaves during winter (i.e. it is deciduous). It has one or more trunks usually growing up to 18 m tall, or rarely reaching up to 25 m in height.

Distinguishing Features

• an upright and spreading tree that loses it leaves during winter.
  
  
• its greenish-brown younger stems soon become hairless and readily become detatched.
  
  
• its alternately arranged leaves (8-17.5 cm long and 1.5-4.0 cm wide) are elongated in shape with irregularly-toothed margins.
  
  
• separate male and female flowers are borne on separate plants, with the new leaves in spring.
  
  
• both types of flowers lack any petals or sepals and are borne in elongated clusters on short side-branches in the upper leaf forks.
  
  
• its small capsules (4-5 mm long) contain tiny seeds topped with a tuft of silky hairs.

Stems and Leaves

The older stems are covered in a pale greyish-brown to dark brown coloured bark that eventually becomes rough and deeply fissured. The younger stems are dark greenish-brown in colour and usually held in an upright position (i.e. erect). They are initially sparsely hairy, but soon become hairless (i.e. glabrescent). These stems are brittle at the point of attachment, and readily become detatched.

The leaves are alternately arranged along the stems and borne on short stalks (i.e. petioles). These leaves (8-17.5 cm long and 1.5-4.0 cm wide) are elongated in shape (i.e. lanceolate or narrowly-ovate) with irregularly-toothed margins and pointed tips (i.e. acute apices). Their upper surfaces are dark green and hairless (i.e. glabrous) while their undersides are paler green or bluish-white in colour (i.e. glaucous) and soon become hairless (i.e. glabrescent).

Flowers and Fruit

Separate male and female flowers are borne on separate plants, with most plants in Australia being male. These inconspicuous flowers are arranged in elongated clusters (i.e. catkins) that are produced at the tips of very short side-branches. Both types of flowers lack petals and sepals, and each flower is subtended by a small bract. The male flowers are greenish-yellow in colour and arranged in relatively broad clusters (4-7 cm long and 10-13 mm wide). The much less common female flowers are greenish in colour and arranged in narrower clusters (5.5-8 cm long and about 7 mm wide). The flowers are produced with the new leaves in early spring.

The small capsules (4-5 mm long) contain tiny seeds, each of which is topped with a tuft of silky hairs.

Reproduction and Dispersal

This species reproduces by seed and vegetatively via the rooting of detached twigs or branches.

The light and fluffy seeds are easily dispersed by wind and water. The twigs readily detach where they join to the branches and may be spread during floods, by machinery, during removal, and in dumped garden waste.

Environmental Impact

Crack willow (Salix fragilis) is regarded as an environmental weed in Victoria, the ACT, Tasmania and New South Wales. It is one of the willows that, as a group, are regarded as a Weed of National Significance (WoNS). These species are primarily of concern along waterways, in wetlands and around other waterbodies. They compete strongly for space, water and nutrients, eventually displacing the native vegetation in the habitats they invade.

Crack willow (Salix fragilis) is actively managed by community groups in Tasmania. It also freely hybridises with related species, especially golden willow (Salix alba var. vitellina), with the resulting hybrids sometimes being even more invasive (e.g. Salix x rubens).

For more on the environmental impact of willows (Salix spp.) in Australia, see Victorian Department of Sustainability and Environment Landcare Note entitled "Willows along watercourses: their impact compared to natives", which is avialable online at http://www.dpi.vic.gov.au.

Legislation

This species is declared under legislation in the following states and territories:

• ACT: C2 - a pest plant that must be suppressed, and C4 - prohibited pest plant (a pest plant whose propagation and supply is prohibited).
  
  
• New South Wales: Class 5 - a restricted weed which must not be sold, bought or knowingly distributed (throughout the entire state).
  
  
• Northern Territory: A - to be eradicated (throughout all of the Territory) and, C - not to be introduced into the Territory.
  
  
• Queensland: Class 1 - introduction into the state is prohibited, and landowners must take reasonable steps to keep land free of this species (throughout the entire state). It is also illegal to sell a declared plant or its seed in this state.
  
  
• South Australia: 11+ - Class 11 is a category for those species that are 'Weeds of National Significance' but are not otherwise declared in South Australia. Control of this species is not currently required, but its sale is restricted throughout the state.
  
  
• Tasmania: D - the importation or sale of this species is prohibited and measures to reduce its population in an area, eradicate it from an area, or restrict it to a particular area may be required.
  
  
• Victoria: R - a restricted weed that cannot be sold or traded in this state.
  
  
• Western Australia: P1 - trade, sale or movement into the state prevented, and P2 - to be eradicated (throughout the entire state).

Management

For information on the management of this species see the following resources:

• a wide variety of resources, including the National Management Guide for Willows, is available online at http://www.weeds.org.au/WoNS/willows/.
  
  
• the Victorian Department of Sustainability and Environment Landcare Note entitled "Willows along watercourses:
  managing, removing and replacing", which is available online at http://www.dse.vic.gov.au.
  
  
• the Greening Australia Willow Control fact sheet, which is available online at http://www.greeningaustralia.org.au.

Similar Species

Two forms of Salix fragilis are present in Australia (i.e. the much more common Salix fragilis var. fragilis and the less common Salix fragilis var. furcata), but these are not always recognised as being separate entities. They can be distinguished from each other by the followng differences:

• Salix fragilis var. fragilis  has unbranched flower clusters.
  
  
• Salix fragilis var. furcata has flower clusters that are divided in two or three (i.e. bifurcate or rarely trifurcate).

Crack willow (Salix fragilis) is also confused with some of the other willows (Salix spp.) with tree-like habits, and hybrids between this and other species can be extremely difficult to separate from each other. To distinguish between these, see one of the texts specifically developed for the identification of willows (Salix spp.) in Australia:

• the Victorian Department of Sustainability and Environment Willow Identification Guide, which is available online at http://www.dpi.vic.gov.au.
  
  
• the Weeds of National Significance Willow Identification resource sheet, which is available online at http://www.weeds.org.au/WoNS/willows/docs/Willow_identification-Resource_Sheet2.pdf.
  
  
• the Key to Willows (Salix) in Rural Australia, which is available online at http://www.hoadley.net/cremer/willows/docs/key2.DOC.