Green alder

''Alnus alnobetula'' is a common tree widespread across much of Europe, Asia, and North America.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 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 flowers are catkins, 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, some treated as separate species by some authors:
*''Alnus viridis'' subsp. ''viridis'' – Central Europe
*''Alnus viridis'' subsp. ''suaveolens'' – Corsica (endemic)
*''Alnus viridis'' subsp. ''fruticosa'' – Northeast Europe, northern Asia, northwestern North America
*''Alnus viridis'' subsp. ''maximowiczii'' (''A. maximowiczii'') – Japan
*''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 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