Growing up to the forest line in the north, grey alder is an important pioneer species in the wild. Growing shrub-like at first, during its relatively short life it can reach almost 20m in fertile soil. By dropping its leaves while still green and fixing atmospheric nitrogen in its roots, grey alder improves the soil of sites like worked-out sand and gravel pits. It also provides an excellent protective canopy for less hardy species.
Grey alder differs from common alder in having dull green leaves downy on both surfaces, and an attractive patchy grey trunk. The species releases pollen from its yellow male catkins starting in February through to late April, before leaf flush. The female flowers, called cones in the vernacular, are an added irritant to fishermen cleaning their nets.
Variation in leaf form has produced several different varieties. Most of them are finely lobed, like that growing at Mustila, which is A. incana ‘Laciniata’.