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{{Taxobox
| color = lightgreen
| name = Grey Alder
| image = Alnus incana rugosa leaves.jpg
| image_width = 240px
| image_caption = Speckled Alder ''Alnus incana'' subsp. ''rugosa''
| regnum = [[Plant]]ae
| divisio = [[flowering plant|Magnoliophyta]]
| classis = [[dicotyledon|Magnoliopsida]]
| ordo = [[Fagales]]
| familia = [[Betulaceae]]
| genus = ''[[Alder|Alnus]]''
| species = '''''A. incana'''''
| binomial = ''Alnus incana''
| binomial_authority = ([[Carolus Linnaeus|L.]]) [[Conrad Moench|Moench]]
}}

The '''Grey Alder''' or '''Speckled Alder''' (''Alnus incana'') is an [[alder]] with a wide range across the cooler parts of the [[Northern Hemisphere]]. It is a small to medium size [[tree]] 15-20 m tall with smooth grey bark even in old age, its life span being a maximum of 60-100 years. The [[leaf|leaves]] are matt green, ovoid, 5-11 cm long and 4-8 cm broad. The [[flower]]s are [[catkin]]s, appearing early in spring before the leaves emerge, the male catkins pendulous, 5-10 cm long, the female catkins 1.5 cm long and 1 cm broad when mature in late autumn. The [[seed]]s are small, 1-2 mm long, light brown with a narrow encircling wing. The Grey Alder has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers, especially in the northern parts of its range.

The Grey Alder is a light-demanding, fast-growing tree that is very tolerant and grows well on poorer soils. In central Europe, it is a colonist of alluvial land alongside mountain brooks and streams, occurring at elevations up to 1500 metres. However, it does not require moist soil, and is a colonist of screes and shallow stony slopes. It is sometimes used for afforestation on non-fertile soils which it enriches by means of its nitrogen-fixing nodules. The wood resembles that of the common alder, but is somewhat paler and of little value.

There are four to six subspecies, some treated as separate species by some authors:
*''Alnus incana'' subsp. ''incana'' (Grey Alder). Northern [[Europe]] and northwestern [[Asia]], and central and southern Europe in mountains, mainly in the regions of the [[Alps]], [[Carpathian |Carpathians]] and the [[Caucasus]].
*''Alnus incana'' subsp. ''hirsuta'' (''A. hirsuta''; Manchurian Alder). Northeastern [[Asia]], and central Asia in mountains.
*''Alnus incana'' subsp. ''kolaensis''. Subarctic northeast Europe.
*''Alnus incana'' subsp. ''oblongifolia'' (''A. oblongifolia''; Arizona Alder). Southwestern [[North America]].
*''Alnus incana'' subsp. ''rugosa'' (''A. rugosa''; Speckled Alder). Northeastern [[North America]].
*''Alnus incana'' subsp. ''tenuifolia'' (''A. tenuifolia''; Thinleaf Alder or Mountain Alder). Northwestern [[North America]].

Several species of [[List of Lepidoptera which feed on Alders|Lepidoptera]] use Grey Alder as a food plant.

==References==
*[http://rbg-web2.rbge.org.uk/cgi-bin/nph-readbtree.pl/feout?FAMILY_XREF=&GENUS_XREF=Alnus&SPECIES_XREF=incana&TAXON_NAME_XREF=&RANK= Flora Europaea: ''Alnus incana'']
*[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500033 Flora of North America: ''Alnus incana'']

[[Category:Betulaceae]]
[[Category:Flora of Estonia]]
[[Category:Trees of Canada|Alder, Grey]]
[[Category:Trees of Western United States|Alder, Grey]]