Created 20-Aug-16
Modified 20-Aug-16
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Alnus glutinosa

European Alder

New Zealand Status: Introduced
Conservation Status: n/a

Alnus glutinosa is a tree that grows to a height of about 20 metres. The bark of young trees is greenish-brown and smooth while in older trees it is dark grey and fissured. The buds are purplish-brown with short stalks. The leaves are short-stalked and rounded, up to about 100mm long with a slightly wedge-shaped base and a wavy, serrated margin. The upper surface is a glossy dark green and the underside is a paler green with rusty-brown hairs in the angles of the veins.

Male and female catkins form in autumn and remain dormant during the winter. Male catkins are slender, pendulous, reddish in colour and 50 to 100 mm long. The wind polinated female flowers are upright, broad and green, with short stalks. During the autumn they become dark brown, hard and somewhat woody cones.

Alnus glutinosa prefers damp or wet soils in a cool to moderate climate and grows well in poor quality soils. It can rapidly seed into open sites and in New Zealand it's considered to be a weed.
Alnus glutinosa, European Alder Branchlet with cones