Grey Alder

Grey alder (Alnus incana) is a fast-growing, deciduous tree or large shrub with a narrow, upright outline, dark-green leaves, and conspicuous catkins. It flowers before leaf emergence, with yellow-brown male catkins appearing in late winter or early spring; cone-like fruits follow in summer. Use it where a quick-growing screen or bank-stabilizing tree has room to mature ([RHS](https://www.rhs.org.uk/plants/901/alnus-incana/details), [RHS Plants](https://www.rhsplants.co.uk/plants/_/alnus-incana/classid.2000048021/)). ## Form and placement The RHS describes a tree to about 20 m high and wider than 8 m; the nursery profile gives eventual dimensions around 20 m by 10 m. The live catalog values and labels fall within these broad source descriptions and are retained. The broad species name includes distinct North American subspecies, including speckled alder and thinleaf alder, so local provenance can affect its mature form and site fit ([USDA Forest Service](https://research.fs.usda.gov/feis/species-reviews/alninc)). ## Growing conditions Grow in full sun or part shade in moist, well-drained soil. Grey alder also tolerates heavy or poor soils and seasonally wet ground, and the RHS notes tolerance of dry conditions after establishment. Its nitrogen-fixing root association can enrich soils as roots and leaves decompose. ## Maintenance Water during prolonged dry periods while young. Once established, the tree generally needs little routine care; remove dead, damaged, or overcrowded growth in late autumn or winter. Avoid hard pruning on mature trees. If a single-trunk form is needed, select and train one stem while young.