Vascular Plants of North Carolina
Account for Green Alder - Alnus crispa   (Aiton) Pursh
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Section 6 » Family Betulaceae
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Author(Aiton) Pursh
DistributionThis is a strongly disjunct species to NC, and in the southern Appalachians is found only on Roan Mountain in Avery and Mitchell counties (and in neighboring Carter County, TN). A report from McDowell County, from a xeric bald, may represent an escape or a misidentification.

This is a far Northern species (with several subspecies), ranging all across Canada from Atlantic to Pacific. However, it ranges southward only to MA, northern NY and MN, with a few scattered records in PA and Roan Mountain in NC and TN. The NC population is at least 400 miles disjunct to the south, as it has never been found in MD, WV, or VA.
AbundanceThough very rare in the state, it is a common shrub on the exposed grass and shrub balds at Roan Mountain, close to the state line. Biologists should easily see the species by walking eastward on the Appalachian Trail from Carvers Gap (NC 261). This is a State Special Concern species.
HabitatThis species occurs at a high elevation – essentially over 5000 feet – in several habitats on Roan Mountain. It grows mainly as clumps of shrubs amid the grass balds, but also forms thickets and thus forms parts of shrub balds, and also occurs at the margins of spruce-fir forests.
PhenologyBlooms in May and June, and fruits in July.
IdentificationThis is a small, deciduous shrub with alternate leaves, usually only 4-6 feet tall. Its leaves are about the same size and shape, and have the same venation pattern, as those of Alnus serrulata. It can be separated from that species mainly by elevation and habitat; it also flowers about the same time as the leaves emerge, whereas A. serrulata has the catkins in bloom in late winter or very early spring before the leaves emerge. Anyone familiar with the very common and widespread A. serrulata will instantly recognize A. crispa at our high elevations.
Taxonomic CommentsThis alder has been moved around between A. crispa and A. viridis ssp. crispa for decades. Weakley (2015) and NatureServe listed it as the latter, but his revised flora (2018) has it moved to A. crispa. The iNaturalist website lists it as A. alnobetula ssp. crispa.

Other Common Name(s)Mountain Alder
State RankS1
Global RankG5
State StatusSC-V
US Status
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B.A. SorrieMitchell County, same data. MitchellPhoto_natural
B.A. SorrieMitchell County, 2004, Roan Mountain near summit. MitchellPhoto_natural

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