Crack willow
Botanical Name
Salix x fragilis
Family
Salicaceae (willow)
Where is it originally from?
Northern temperate regions
What does it look like?
Deciduous tree (<25 m), occasionally only shrub size, with spreading rather than hanging branches, and rough and fissured bark. Roots sucker and rootlets are bright red when in or near water. Dark or brownish green shoots are not slender, and snap with a loud crack when bent. Bud scales are shiny and dark brown. Shoots and leaves are silky when young but become hairless as they mature. Lance-shaped leaves with tiny serrations are bluish underneath and the upper surface is shiny and often covered with bright red galls. Narrow downward curving catkins (40-75 mm long) appear at the same time or after the leaves, from September to October. As there are only male plants in New Zealand, no fruit is formed.
Are there any similar species?
Many Salix species are similar including hybrids of S. fragilis.
Why is it weedy?
Resprouting and suckering habit and rapid growth creates dense thickets. Tolerates flooding, hot to cold, most soils, and semi-shade.
How does it spread?
Stem fragments are spread by water, and suckers spread locally. Planted intentionally on stream and river banks and also in damp places to absorb water.
What damage does it do?
Replaces native species in riparian sites and forms vast dense (often pure) stands along channels. Causes blockages, flooding and structural changes in waterways.
Which habitats is it likely to invade?
Stream and lake edges, and river systems, throughout New Zealand.
What can I do to get rid of it?
Begin control at top of catchment, treat every stem.
1. Cut and squirt (summer-autumn) or bore and fill: Make 1 cut or hole every 100 mm around the trunk and saturate each cut or hole with 10ml glyphosate (undiluted).
2. Frilling (summer-autumn): glyphosate (100ml/L).
3. Spray (full leaf stage only): glyphosate (12.5ml/L + penetrant, total coverage needed) or metsulfuron-methyl 600 g/kg (5g/10L in December).
What can I do to stop it coming back?
Almost all cut stems root where they fall. Cut stumps regrow rapidly. Do not fell unless all plant material can be disposed of at a refuse transfer station or by burning. Best to poison while standing to avoid live stem contact with ground. Prevent grazing and other disturbance. Interplanting can follow if non-spray follow up control options used.
