Crack willow

Salix x fragilis

Also known as: Hybrid willow
Pest group: Plants
Pest type: Shrubs and trees

Crack willow is a shrub or tree no taller than 25m. It gets its name from the cracking sound it makes when bending. It displaces native species and alters waterways by blocking and flooding.


  • Stems are dark brown/green and snap with a crack when bent.
  • Leaves are lance-like and less than 15 x 2.5cm.
  • Flower clusters with no petals (catkins) are less than 7.5cm long and appear with or after leaves in spring.
  • Vegetative spread from stem fragments and suckers, dispersed by water.
  • Human-mediated dispersal through deliberate plantings.
  • Habitat includes wetlands, water bodies, water body margins, swamps, and wet areas behind coastal dunes.

What you need to know

Forms dense stands that compete with and displace native species. Alters hydrology of waterways through blocking, flooding and structural changes. May alter soil decomposition cycles.

Management approach

Crack willow is an unwanted organism regulated under the National Plant Pest Accord.

National Pest Plant Accord (NPPA)

The NPPA prevents the sale, distribution and propagation of specified pest plants within Aotearoa/New Zealand and is administered by the Ministry for Primary Industries (MPI).


Any species declared a pest, including unwanted organisms, cannot be sold or be in a place where plants are being sold. Pest plants cannot be propagated, bred, multiplied, communicated, released, caused to be released, or otherwise spread.

See the MPI website for more information on the NPPA.

Consider removing this invasive species from your property and consult your local council for appropriate disposal. Consider lower-risk alternatives for your garden, such as native plants.


Site management

Follow up treated areas three times per year. Encourage natural regeneration of native plants or replant treated areas where possible after two to three treatments to establish dense ground cover and minimise reinvasion.

Physical control

Dig or pull small plants out.

Plant parts requiring disposal: all parts.

Contact your local council for appropriate disposal locations.

Chemical control

No qualifications: Cut stump and paste freshly cut base of stems with glyphosate gel or spray freshly cut base with 250ml glyphosate per 1L of water. Cut material must be removed or it will regrow.

Certified handler/experienced agrichemical user: Drill and inject trees with 500ml glyphosate per 1L of water if safe to do so. Drill 18mm holes (tangentially angled downwards) in a spiral up the trunk. For 100mm stems drill two holes. For larger stems drill holes 150mm apart. Foliar spray with 150ml glyphosate per 10L of water and 20ml penetrant.

Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

Biological control

Biological control is currently not available for this species.