Weed Watch – Grey Willow

Grey willow (Salix cinerea) belongs to the Salicaceae (willow) family and is also known as Pussy willow. It is one of the willow species creating the greatest challenges to biodiversity. Its impacts include the ‘crowding out’ of indigenous plants, disruption to natural waterway functions through blockage and the uptake of water. It spreads aggressively and forms dense thickets that exclude native species. It can tolerate flooding, hot and cold temperatures and semi-shade conditions.

Originating in Europe, West Asia and North Africa, grey willow is now found throughout New Zealand. In Canterbury it is found in wetlands, riverbanks, wet areas behind sand dunes and in nearby drier alluvial areas. It spreads through seed dispersal, with seeds travelling many kilometres on the wind. It can also spread from fragments.

Grey willow catkin/ flower - maleIt is a deciduous tree that grows to 7 metres in height. Its non-brittle stems are grey or greenish-grey and hairy, or reddish to dark purple. Leaves are shiny on the upper side and covered with grey hairs underneath. Plants are either male or female, with flowers (September-October), appearing as catkins – often before the spring leaves. Male catkins have yellow-tipped ‘hairs’ (sometimes called antlers), the females do not.

The best methods of control include pulling out the seedlings, or cutting and painting larger plants with herbicide. Use all herbicides in accordance with the manufacturer’s instructions and ensure no herbicide comes into contact with other plants, soil or waterways. For large infestations, target removal of female plants first to reduce long-distance spread. Make sure all plant material is placed in an appropriate landfill – don’t include it in compost or leave it lying around.

For further information contact weeds@ecan.govt.nz.