Alnus glutinosa, the common alder, also referred to as the European alder, black alder or just ‘Alder’ is a species of tree from the Betulaceae family, it is found in much of Europe, North Africa and even southwest Asia.
It grows best in wet locations and is able to grow in various soil types. It is a short lived tree of medium size, growing to a height of around about 100 ft. It has short stalked leaves which are rounded and flowers via catkins.
They produce small, fruits which are cone-like and the seeds as with most trees are distributed by wind and water. The common alder is useful to wildlife both as as source of food and shelter. A number of insects species have grown to depend on the tree along with some fungi.
It is quite a resilient species, colonizing vacant land allowing others trees to come after it forming mixed forests. Common alders tend to be found on forest edges rather then in the center of woodlands due to seedling light requirements. It is also found in swamps and riverside corridors.
Uses of The Alder Tree
The timber has been used for a variety of applications including underwater foundations and for manufacture into paper. It is also used in some folk remedies for various ailments, and extracts of the seeds are believed to help against pathogenic bacteria.
Alnus glutinosa thrives in moist soils, and can grow as large as 66 to 98 ft typically the largest example know was 121 ft. Young trees growth with a main axial stem but then develop an arched crown over time comprising of crooked branches. The base of the trunk can produce roots which grow down towards the soil appearing to be propping up the trunk.
When the tree is young The bark is smooth and greenish brown, older trees however it changes becoming dark grey and fissured. The branches are smooth and the buds are purplish brown with short stalks. Catkins form in the autumn and are dormant in the winter. The common alder has leaves that are rounded, short-stalked and up to 4 in long.
They have a dark green surface and a pale green underside with rusty brown hairs. Like some other trees growing near water, this tree keeps its leaves longer than do trees in drier habitats, and the leaves remain late into the autumn. The buds and young leaves are sticky with a sort of resinous gum.
The flowers are wind pollinated; the male catkins are somewhat pendulous, red in colour and 2 to 4 in long; the female flowers are upright and broad and green. During the autumn they become hard and change color to a dark brown dark brown, somewhat woody and on the surface similar to small conifer cones.
They ride out the winter and the small seeds are scattered the following spring. The seeds are reddish brown nuts edged with a kind of webbing filled with air pockets. This enables them to float longer ensuring the seeds disperse widely. Common alders do not produce shade leaves. with alders as a tree in woodland grows taller, the lower branches tend to die and then decay, leaving a small crown with an unbranched trunk.
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