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’.