''Alnus alnobetula'' is a common tree widespread across much of Europe, Asia, and

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

.Kew World Checklist of Selected Plant Families
/ref> Many sources refer to it as ''Alnus viridis'', the green alder, but botanically this is considered an illegitimate name synonymous with ''Alnus alnobetula'' subsp. ''fruticosa''.

Description

It is a large

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

or small tree tall with smooth grey bark even in old age. The

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

are shiny green with light green undersurfaces, ovoid, long and 2–6 cm broad. The flowers are

catkin A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind-pollinated (anemophilous) but sometimes insect-pollinated (as in ''Salix''). They contain many, usually unisexual flowers, arranged cl ...

s, appearing late in spring after the leaves emerge (unlike other alders which flower before leafing out); the male catkins are pendulous, 4–8 cm long, the female catkins 1 cm long and 0.7 cm broad when mature in late autumn, in clusters of 3–10 on a branched stem. The seeds are small, long, light brown with a narrow encircling wing. The roots of ''Alnus viridis subsp. sinuata'' have nitrogen-fixing nodules. A study in Alaska showed that Sitka alder seedlings were able to invade coal mine spoils and can be used for revegetation and stripmine reclamation.

Distribution

There are four to six

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

, some treated as separate species by some authors: *''Alnus viridis'' subsp. ''viridis'' – Central Europe *''Alnus viridis'' subsp. ''suaveolens'' –

Corsica Corsica ( , Upper , Southern ; it, Corsica; ; french: Corse ; lij, Còrsega; sc, Còssiga) is an island in the Mediterranean Sea and one of the 18 regions of France. It is the fourth-largest island in the Mediterranean and lies southeast of ...

(endemic) *''Alnus viridis'' subsp. ''fruticosa'' – Northeast Europe, northern Asia, northwestern

*''Alnus viridis'' subsp. ''maximowiczii'' (''A. maximowiczii'') –

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

*''Alnus viridis'' subsp. ''crispa'' (''A. crispa'', mountain alder) – northeastern North America, Greenland *''Alnus viridis'' subsp. ''sinuata'' (''A. sinuata'', Sitka alder or slide alder) – western North America, far northeastern Siberia ''Alnus viridis'' is classed as an environmental weed in New Zealand.

Ecology

''Alnus viridis'' has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers. ''Alnus viridis'' is a light-demanding, fast-growing shrub that grows well on poorer soils. In many areas, it is a highly characteristic colonist of avalanche chutes in mountains, where potentially competing larger trees are killed by regular avalanche damage. ''A. viridis'' survives the avalanches through its ability to re-grow from the roots and broken stumps. Unlike some other alders, it does require moist soil, and is a colonist of screes and shallow stony slopes. It also commonly grows on subarctic river gravels, particularly in northern Siberia, Alaska and Canada, occupying areas similarly disrupted by ice floes during spring river ice breakup; in this habitat it commonly occurs mixed with shrubby willows.

Uses

It is sometimes used for

afforestation Afforestation is the establishment of a forest or stand of trees (forestation) in an area where there was no previous tree cover. Many government and non-governmental organizations directly engage in afforestation programs to create forests a ...

on infertile soils which it enriches by means of its nitrogen-fixing nodules, while not growing large enough to compete with the intended timber crop. ''A. sinuata'' can add 20 kg of nitrogen per acre (50kg/hectare) per year to the soil. ''Alnus viridis'' leaves have been used in the traditional Austrian medicine externally or internally as tea for treatment of infections and fever.

References

External links

''Alnus viridis''
- information, genetic conservation units and related resources. European Forest Genetic Resources Programme (EUFORGEN) {{Taxonbar, from1=Q20720096, from2=Q163978 alnobetula Trees of North America Trees of Europe Trees of Asia Flora of the Alps Flora of the Carpathians