Alnus incana

Grey alder


The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Magnoliophyta ( Flowering plants). Class - Magnoliopsida. Order - Fagales. Family - Betulaceae (Birch family). Genus -Alnus Mill. Species - Alnus incana (L.) Moench

Ecology: Alnus incana is a light-demanding, fast-growing tree that grows well on poorer does not require moist soil, and will also colonize screes and shallow stony slopes.It is sometimes used for afforestation on non-fertile soils which it enriches by means of nitrogen fixing bacteria in its root nodules.


Grey alder (Alnus incana), trees and shrubs , to 25 m; crowns open. Bark light to dark gray, reddish, or brown, smooth, or in age broken into irregular plates; lenticels present or absent, conspicuous, enlarged or unexpanded. Winter buds stipitate, ellipsoid, 4--7 mm, apex rounded to nearly acute; stalk 1--3 mm; scales 2--3, equal, valvate, resin-coated. Leaf blade narrowly ovate to elliptic, base cuneate to narrowly rounded, margins doubly serrate, with distinctly larger secondary teeth, apex acute or short-acuminate to obtuse. Inflorescences formed season before flowering and exposed during winter. Flowering before new growth in spring. Infructescences ovoid to nearly cylindric; peduncles relatively short and stout. Samaras elliptic to obovate, wings narrower than body, irregular in shape.


Grey alder has relatively few major threats in the way of pests and diseases, although older stems are prone to decay by a number of fungus species


Flowering and Fruiting- Flowering occurs in early spring (March–May), before the leaves appear, the inflorescences formed in late summer the season before flowering. Fruit maturation is in late August–September with the seeds dispersed the following spring.

Propagation by Seed: can be propagated by seed or by cuttings. Seeds are shaken from dried cones collected in September and October and can be stored air-dry in sealed containers for several years. They are most easily sown in a cold frame immediately after ripening, in sand or a sandhumus mixture. Spring planting of seeds collected earlier requires stratification in moist sand or vermiculite for 60-90 days at 5° C. Seedbeds should be kept moist and shaded until late in the summer. Germination rates are often low. Softwood cuttings taken in summer, treated with rooting promoter, and rooted under mist provide good starts; cuttings of mature wood taken soon after leaves fall also are reported to be effective. Two or three year-old seedlings are used for field planting.

Species Distribution


The Jepson Herbarium
Burns, R.M., and B.H. Honkala. 1990. Silvics of North America (Volume 1: Conifers, Volume 2: Hardwoods). USDA Forest Service Agricultural Handbook 654.

USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

Flora of North America
Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 19+ vols. New York and Oxford.

Burke Museum of Natural History and Culture
Burke Museum. 2016. Abies amabilis [Online]. University of Washington.