Crack willow

Crack willow is a large (<25 metres) deciduous tree (very occasionally a shrub) with branches that spread, rather than hang, with fissured bark.

Description

• Leaves and shoots are silky when young and become hairless on maturity. Upper surface is shiny and often covered with bright red galls.

• Brownish-green shoots that snap loudly when bent.

• Catkins are 40-75mm long and appear from September – October.

• No fruit is formed as there are only male plants in New Zealand.

• Roots sucker and rootlets are bright red when in or near water.

• Stem fragments are spread by water and suckers spread locally.

What you need to know

Crack willow replaces native vegetation in riparian sites and grows into dense (often pure) stands. Thick canopies can reduce light penetration and limit the growth of understory species. It can also cause blockages, flooding and structure changes in waterways.

Management approach

Crack willow is declared an unwanted organism by the Ministry for Primary Industries (MPI) because it is capable of causing harm to the natural environment, physical resources or human health in Aotearoa/New Zealand.

These species pose a high risk to our environment, economy, recreation, and cultural values.

Rules

Any species declared a pest 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.

To help protect our environment:

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.

Control

Physical control

Dig or pull-out small plants and seedlings

Plant parts requiring disposal: all parts

Contact your local council for appropriate disposal options

Chemical control

Cut plant close to the ground and immediately treat the stump with herbicide gel containing glyphosate.

Basal spray with X-Tree Basal - apply from the ground to a height of six times the diameter of the tree, ensure the base is thoroughly covered at ground. Suitable for trees up to 20cm in diameter.

Drill downward sloping holes around the circumference of the trunk about 8-10 cm apart. Fill with neat or 250ml glyphosate (120g/L).

Foliar spray with 20ml glyphosate plus 2ml penetrant per 1L of water.

Foliar spray with 0.5g metsulfuron-methyl plus 3ml penetrant per 1L of water.

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