Alder (Alnus glutinosa)
Common Alder, Black Alder, Irish Fearnog (Family:Betulacae)
Description: Rapidly growing tree (0.5m pa for first 30 - 40 years) mature at about 60 years with long trunk and narrow crown. Distinctive outline in winter. Requires plenty of light and can be used as pioneer species. Height 20m or more. Age up to 150 years.
Where found: Very tolerant of water logged conditions whilst dormant. Typical streamside tree and as a specific habitat - Alder Carr - in Lake District and Norfolk Broads. All soil types except poor acid peats. Fixes nitrogen via root nodules and will grow on relatively infertile soils and hence used for site reclamation. Natural throughout British Isles
Common or black alder occurs throughout most of Europe and across Russia to Siberia. Its range also includes the Caucasus, Iran, Turkey and North Africa, where it is native to Tunisia, Algeria and Morocco. It has been introduced to North America, probably during colonial times, and has become naturalised in eastern Canada and the northeast of the USA.
Alder is found throughout Scotland, although its presence in Shetland is due to planting. Today it is rare in the Outer Hebrides and the far northwest of the mainland, but this is the result of deforestation, rather than a limit in the tree's range. Alder occurs at elevations of up to 500 metres and typically grows alongside streams and rivers, or on wet ground. As a result it is often found in narrow bands along watercourses, although in the right conditions it can form alder carr, which is a dense thicket or stand of alder, usually small in height, growing on wet swampy soils.
Alder is a member of the birch family of trees, Betulaceae, and can reach 25 metres in height, although in Scotland it is rarely more than 20 metres tall. Like the birches, it is a pioneer species which grows quickly and is relatively short-lived, with the maximum age typically being 150 years. The annual rate of growth can be up to 90 cm. a year when the tree is young, and after the death of the original trunk, new shoots can sprout from the base, forming a multi-stemmed clump of new growth.
