A deciduous tree of height up to 15m or so often branching above the base. The Tree likes wet conditions and grows close to high water-tables and is common along streamsides and in marshland.
The leaves are oval, 3-9 cm long and broadest towards the tip. They are borne alternately on the twigs. They are almost hairless, Dentate - with fine teeth along the margins and are slightly sticky when young. The upper side is dark green but the lower side is paler. The leaf stalk is 1-3 cm long..Leaves often have small blisters on the upper surface caused by tiny mites
The male catkins open on the same trees in spring, before the leaves, but soon fall.
The bark is rough and often sprouts young shoots.
Alders should have numerous small black, woody cones approximately 2 cm long persisting for several years. These started as female catkins each scale of which held two dark brown seeds.The seeds are edged with air-filled tissue which enables them to float on water for about a month
Wood is easy to work with and has been used to make clogs, toys and pencilsAlder was used to make charcoaland was used to manufacture gunpowder as late as 1946.