Trees Planet: Alnus incana

Thursday, August 15, 2013

Alnus incana - Grey Alder

General Information

Common Name	Grey Alder
Scientific Name	Alnus incana
Sun Tolerance	Full Sun
Height	16–22 m (50–70 ft)
Spread	6–9 m (20–30 ft)
Growth Rate	Fast
Bloom Time	Spring
Color	Green
Flower Color	Yellow, Red
Type	Tree
Native	Europe, North America

Classification

Kingdom	Plantae – Plants
Subkingdom	Tracheobionta – Vascular plants
Superdivision	Spermatophyta – Seed plants
Division	Magnoliophyta – Flowering plants
Class	Magnoliopsida – Dicotyledons
Subclass	Hamamelididae
Order	Fagales
Family	Betulaceae – Birch family
Genus	Alnus Mill. – alder
Species	A. incana

Alnus incana - Grey Alder

The Grey Alder, Scientific Name is Alnus incana is introduced from Central Europe in 1780, is distinguished from the native Alder, A. glutinosa (L.) Gaertn, by its grey bark, downy young shoots, and pointed leaves, grey beneath, and its tendency to sucker vigorously. It thrives on even fairly dry areas and has been chosen for illustration because it is less common.

The native Alder is a moderately-sized tree with a narrow crown and short, spreading branches and grows in moist places, usually alongside streams, river, ponds and lakes.

Its winter buds, borne alternately o reddish-brown twigs which are rather tacky in their green state, are distinctly stalked and have a purple waxy bloom. The alternate leaves ( about 2-3 in broad and long) are either round or slightly obcordate, they are dark green, have a toothed margin, and are slightly tacky as they unfold, hence the specific name, glutinosa, sticky. Both sexes of flowers are borne on the same tree, before the leaves open. The male catkins are oblong, drooping, purplish or reddish-brown becoming yellow, and about an inch long. The female catkins are small, cylindrical and purplish-brown, after pollination they enlarge to a green oval or spherical shape, later becoming a brown woody cone-like structure about half an inch long, which opens during the wintr permitting the numerous small winged seeds to escape. Many of the empty ‘cones’ persist on the tree well into spring. At first the bark is fairly smooth and greenish-brown, but later becomes fissured and dark grey. A height of over 75 feet can be attained, the tree is usually harvested before this, whereupon coppice shoots arise from the stool.

Alnus incana - Grey Alder

Alder is rarely planted – it springs up mainly from seeds that have been carried by water. It will grow in conditions of wetness of soil which few trees will tolerate. The timber is reddish, but bright orange when first cut, mellowing to dull brown. The wood is strong and easily worked but not naturally durable. Its uses include paper pulp and turnery goods such as broom heads and cheap tool handles. In earlier days it was valued for soles of clogs and for charcoal used in the manufacture of gun-powder.

An interesting point about Alder is that it bears on its roots curious nodules, like those of leguminous plants, in which live a bacterium, enabling it to take soluble nitrogen salts out of the inert nitrogen of the air, consequently the soils on which Alder grows are remarkable fertile. The tree is sometimes planted as fire-break in plantations.