Alnus viridis (Green Alder) is an alder with a wide range across the cooler parts of the Northern Hemisphere. It is a large shrub or small tree 3-12 meter tall with smooth grey bark even in old age. The leaves are shiny green, ovoid, 3-8 centimeter long and 2-6 centimeter broad. The flowers are catkins, appearing late in spring after the leaves emerge (unlike other alders which flower before leafing out); the male catkins are pendulous, 4-8 centimeter long, the female catkins 1 centimeter long and 0.7 centimeter broad when mature in late autumn, in clusters of 3-10 on a branched stem. The seeds are small, 1-2 millimeter long, light brown with a narrow encircling wing.