Alnus alnobetula is a common tree widespread across much of Europe, Asia, and North America.[ Kew World Checklist of Selected Plant Families] 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.[Govaerts, R. (2003). World Checklist of Selected Plant Families Database in ACCESS: 1-216203. The Board of Trustees of the Royal Botanic Gardens, Kew.]
Description
It is a large
shrub or small
tree tall with smooth grey bark even in old age. The
leaves are shiny green with light green undersurfaces, ovoid, long and 2–6 cm broad. The
are
, 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
are small, long, light brown with a narrow encircling wing.
The roots of Alnus viridis subsp. sinuata have nitrogen-fixing nodules.
Distribution
There are four to six
subspecies, some treated as separate species by some authors:
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Alnus viridis subsp. viridis – Central Europe
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Alnus viridis subsp. suaveolens – Corsica (endemic)
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Alnus viridis subsp. fruticosa – Northeast Europe, northern Asia, northwestern North America
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Alnus viridis subsp. maximowiczii ( A. maximowiczii) – Japan
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Alnus viridis subsp. crispa ( A. crispa, mountain alder) – northeastern North America, Greenland
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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 , 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 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 .
Uses
It is sometimes used for
forestry 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.
leaves have been used in the traditional Austrian medicine externally or internally as tea for treatment of infections and fever.
External links
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Alnus viridis - information, genetic conservation units and related resources. European Forest Genetic Resources Programme (EUFORGEN)
