Grey Alder has grey bark, and grey pubescent shoots and leaf undersides. Also known as Speckled Alder due to the pale lenticels on its bark, although it is not the only alder species with this trait.

Native to much of north-west Europe and the Caucasus, ranging further north in Scandinavia than Black Alder but absent from the warmer Mediterranean. Subspecies range wider, including subsp. rugosa in North America and subsp. hirsuta in north-east Asia. A neophyte in Britain and Ireland, introduced 1780, widespread but never common and absent from uplands.

Monoecious. Wind-pollinated. Seeds dispersed by wind and water. A fast-growing pioneer species. Short-lived (60–100 years).

Medium-tall (24m), broad and conic, often leaning, multi-stemmed and suckering into dense clonal thickets. Bark grey, sometimes yellowish, thin and fairly smooth with pale lenticel bands, fissuring with age. Twigs grey-downy; buds red-brown, resinous, short-stalked. Leaves 5-10cm, ovate, shallowly lobed and double-serrate, with flat (non-revolute) edges and grey downy undersides. Male catkins 3-10cm; female woody cone-like. Red Alder differs: glabrous, more lobed, revolute leaves.

A light-demanding, fast-growing tree that quickly colonises bare ground, also spreading by root suckers and layering. Moderately drought-tolerant, though less so than Italian Alder. Like other alders, its nitrogen-fixing root nodules improve the fertility of poor soils.

No notable associations where introduced.

Susceptible to Phytophthora alni but less so than Black Alder.

The main value of this species is as an ecosystem engineer. While its timber is of low value, it has some potential for biomass production where its relatively short height also makes it particularly suitable for growing below overhead powerlines.