Alnus alnobetula aka Green Alder

Alnus alnobetula is a shrub in the birch family, Betulaceae. It is deciduous, which means it sheds its leaves. People call it green alder or mountain alder. The name Alnus viridis is a synonym for this species. Its native range spans the north of three continents. These are North America, Europe, and Asia. It grows in temperate zones and cold subarctic lands. Its range includes mountains in the north. It is not native to Great Britain or Ireland.

In North America, it grows across Canada and many northern US states. It also grows in mountains farther south in the United States. These include parts of California, Tennessee, and North Carolina. Oregon State lists it as native or naturalized in Oregon. North America has several named subspecies of this plant. All belong to the wider species described here. Its broad range covers much of the northern world.

The shrub can spread out or have a compact shape. Oregon State reports heights above 32 feet [10 metres]. The supplied sources give no usual garden height or spread. The smooth bark has scattered lenticels, or small surface pores. The winter buds are egg-shaped and have no stalk. Each bud joins straight to the stem. These traits help describe the plant when it is bare.

The leaves can be broad or narrow in outline. Some are egg-shaped; others are elliptic, or oval. Several forms fall between these shapes. Leaf bases can be round or almost heart-shaped. The tips may come to a point or stay round. The edges range from fine teeth to coarse double teeth. This range of shapes is part of the species description. No one leaf outline fits all plants of this species.

The flowers grow in male and female catkins. Male catkins grow alone or in groups of two to four. They form late in the growing season before they bloom. They stay exposed through winter. Female catkins grow alone or in groups of two to ten. These also form in the season before they bloom. In spring, they emerge with the new growth.

The fruit are samaras, a type of winged fruit. Their thin wings are wider than their bodies. Their shape ranges from elliptic to broader toward the tip.