ORIGIN

N. temperate regions

COMMON NAME

Willow

BOTANICAL NAME

Salix spp.

IDENTIFICATION

Mostly deciduous trees and shrubs. Many species are present in New Zealand but often only represented by a single clone. Leaves usually alternate, trunks sometimes lying down and rooting at nodes. Leaves lanceolate or elliptic to oval. Sometimes shallowly toothed. Produces catkins. The main species in Northland is the extremely aggressive crack willow (Salix fragilis) a tree to 25 m, with bright red rootlets in or near water. The branchlets break easily with an audible crack when bent. Nearly all the plants are female. Hybridises. Flowers Sep-Oct.

HABITATS

Riverbanks, lake sides, drainage canals, wet places. Crack willow forms dense stands in rivers and drains and is locally abundant.

IMPACT TO BIOTA AND ECOSYSTEMS

Blocks streams, drains and culverts. Forms dense stands totally excluding native vegetation.

DISPERSAL ROUTES, VECTORS, INFESTATION SOURCES

Brittle and easily broken shoots grow extremely easily. Was introduced during the early days of settlement and spread rapidly.

MANAGEMENT

Physical Control
Hand pull small plants ensuring that all vegetation and roots are removed. Chainsaw and treat stump with herbicide mix.

Disposal
Remove all shoots.

Chemical Control
Consent is required before applying herbicides to a waterway.

(i) Glyphosate.

Rate - Handgun 1 litre Glyphosate + 200 mls Penetrant/10 litres water.

Knapsack 100 mls Glyphosate + 20 mls Penetrant/10 litres water.

(ii) Metsulfuron. Apply from November-April, ensure complete coverage of trees.

Rate - Handgun 35 g Metsulfuron/100 litres water.

Knapsack 5 g Metsulfuron/10 litres water.

(iii) Trunk treat. Drill 15mm holes at 45° angle at 20cm spacings around the trunk. Fill these holes with suitable herbicide mix. A number of herbicides are effective eg. Metsulfuron, Glyphosate and Triclopyr.

Biological Control

Recommended Approach
Hand pull small plants. Trunk treat larger plants.

FURTHER COMMENT