What does it look like?
Grey willow is a deciduous shrub or tree growing up to 7m high. The leaves (20-70 x 15-35 mm) are oval and serrated. Topsides of leaves are shiny, with grey-blue undersides and covered in dense soft grey hairs. It’s often found growing in swamps, riverbanks and wet areas behind coastal dunes. It spreads by seed or by suckering from the roots. Plants are either male or female. Erect cylindrical catkins (15-35 mm long) are produced from September to October before leaves appear. Seed capsules are bivalved and contain many seeds which have fluffy outgrowths and are dispersed by wind.
Why is it a problem?
Grey willow replaces native species in wetlands and can form vast, dense stands. Although it has been widely planted in wet areas for soil reclamation and stabilisation, it can cause blockages, flooding, and structural changes to waterways.
Control methods
Herbicide control
Begin control at top of catchment and treat every stem.
- Cut and squirt (summer and autumn): Make 1 cut every 100mm around the trunk and saturate with undiluted glyphosate (10 ml) or 2,4-D ester (20 ml). Or,
- Cut stump application: Apply picloram gel. Remove all plant material from site as all cut stems can root where they fall. Or,
- Bore and fill (during summer and autumn): Make 1 hole every 100 mm around the trunk and saturate each hole with undiluted glyphosate (10ml) or metsulfuron-methyl 600g/kg (2ml of 20g/L) or undiluted 2,4-D ester (20ml). Or,
- Frilling (during summer and autumn) using glyphosate (100ml/L) or 2,4-D ester (200ml/L). Or,
- Spray (full leaf stage only) using glyphosate (12.5ml/L + penetrant, total coverage needed) or metsulfuron-methyl 600 g/kg (35g/100L from January to April before leaf fall begins).
- 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 cinerea • New Zealand Plant Conservation Network
NPPA and the control of weeds | NZ Government
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
