What does it look like?
Crack Willow is a deciduous tree growing to 25m tall. It has a spreading crown and multiple trunks. Bright red rootlets are present when the plant is in or near water. The shoots are dark-brownish green and snap with a characteristic "crack" when bent. The leaves are lance-shaped with tiny serrations and bluish underside. Narrow downward curving catkins from September to October. As there are only male plants in New Zealand, no fruit is formed.
Why is it a problem?
The roots of crack willow provide protection from flooding by holding banks in place. However, it can form large, dense stands along river and stream channels, displacing native species, choking waterways and increasing the risk of flooding. The branches are very fragile and fragments break off readily. The smallest of fragments will root in mud and produce mature trees wherever conditions are favourable. Its growth and spread is exponential - slow to start with, then very rapid as the population grows.
Control methods
Herbicide control
Begin control at top of catchment and treat every stem.
- Cut and squirt (during sprint and summer) or bore and fill: Make 1 cut or hole every 100 mm around the trunk and saturate each cut or hole with undiluted glyphosate (10ml). Or,
- Frilling (during summer and autumn) using glyphosate (100ml/L). Or,
- Spray (full leaf stage only) with glyphosate (12.5ml/L + penetrant, total coverage needed) or metsulfuron-methyl 600 g/kg (5g/10L in December).
- CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.
Related links
Salix fragilis × S. euxina • New Zealand Plant Conservation Network
Management Programme
National Pest Plant Accord (NPPA)
The NPPA is designed to prevent the sale, distribution and propagation of a set list of pest plants (the Accord list) within New Zealand. If allowed to spread further, these pest plants could seriously damage the New Zealand economy and environment.
More informationUnwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
Taxonomies
FamilySalicaceae
TypePlants
GroupTree
HabitatLand
Management ProgrammeNational Pest Plant Accord (NPPA)Unwanted Organism
