Also known as
European alder, black alder
Where is it originally from?
Eurasia, North Africa
What does it look like?
Deciduous tree to 15m high, with dark brown, fissured bark, often with two or three main trunks growing together. Purple or grey leaf buds turn into leathery, oblong toothed leaves (5-10 cm), with raised veins on the underside and rounded tips. Young leaves and buds are slightly are sticky with a resinous gum. Distinctive long, narrow male catkins made up of many flowers pollinate female catkins, which then develop into woody cones (1-2cm long) which open as they ripen to disperse seeds (3mm) in autumn. Both male and female flowers are found on the same tree, appearing before the leaves. Male catkins are yellow and pendulous (2-6cm long), dangling from the branches, while female catkins are green, small and rounded, and are grouped (3-8) on each stalk. After wind pollination the female catkins develop into green cones that ripen into brown before releasing flat and waxy seeds (nutlets) that float on water.
Why is it weedy?
Fruits prolifically, and forms thickets by suckering, forming dense stands in wet areas.
How does it spread?
Wind, gravity and water. Suckers from the main plant.
What damage does it do?
Invades wet natural areas, forming dense stands and crowding out other species.
Which habitats is it likely to invade?
Moist or waterlogged sites and along rivers.
What can I do to get rid of it?
1. Dig or pull out small plants (all year round).