Alnus crispa (Aiton) Pursh. Green Alder, Mountain Alder. Phen: May-Jun; Jul. Hab: Grassy balds, shrub balds, spruce-fir forests, and rock outcrops at high elevations (1600-1900m) in the Roan Mountain Massif, Mitchell and Avery counties, NC and Carter County, TN. Dist: Greenland to NT south to MA, NY (Adirondacks), n. MI, n. WI, c. MN, SK, and AB; disjunct in montane PA; disjunct on the Roan Mountain massif (Mitchell and Avery counties, NC and Carter County, TN).

Origin/Endemic status: Native

Taxonomy Comments: The "green alder" on Roan Mountain and "green alders" in general have had a complicated and controversial taxonomic and nomenclatural history (see synonymy). The Roan Mountain population has sometimes and in the past been considered a narrowly endemic species (Alnus mitchelliana, the name however not validly published) (Gray 1842), but more usually considered to be a disjunct population of the ne. North American "crispa" entity, which has variously been considered as varietally, subspecifically, or specifically distinct from the typic "green alder" of Europe. The appropriate name for the European green alder, and therefore other taxa treated as subspecies or varieties under it, has also been controversial, with Alnus viridis usually considered the name with priority, but it now seems clear that A. alnobetula has priority over A. viridis (Chery 2015). Most recent authors treat A. alnobetula (the former A. viridis) as a circumpolar complex of several subspecies or varieties, including the ne. North American "crispa". Varietal ranks have also been used, and sometimes North America and e. Asian taxa are separated at specific rank from European. The "viridis" entity occurs in montane portions of Europe. The "sinuata" entity occurs in w. Canada and south in the montane west to nw. United States. The "fruticosa" entity ranges from n. CA north to coastal AK, and in ne. Asia. Several additional entities are limited to e. and ne. Asia and are sometimes included within A. alnobetula as subspecies or varieties, or not, or lumped (Chery 2015; Ren, Xiang, & Chen 2010; Banaev & Adel’shin 2009). The "crispa" entity is generally far northern, ranging in Greenland, n. Canada (NL and NU west to NT), south to MA, c. NY, MI (Upper Peninsula only), WI, MN, MB, SK, and AB, and disjunct at a few localities in PA and at Roan Mountain on the NC-TN border, where it forms an extensive population.

Synonymy: = G, RAB, W, Hardin (1971a); = Alnus alnobetula (Ehrh.) K.Koch ssp. crispa (Aiton) Raus – K4, NY, Chery (2015); = Alnus crispa (Aiton) Pursh ssp. crispa – Banaev & Adel’shin (2009); = Alnus viridis (Vill.) Lam. & DC. ssp. crispa (Aiton) Turrill – FNA3, K1, K3, Mi, NE, Pa, Tn, Furlow (1990); = Alnus viridis (Vill.) Lam. & DC. var. crispa (Aiton) House – C; < Alnus alnobetula (Ehrh.) K.Koch – S, S13; Alnus alnobetula (Ehrh.) K.Koch var. crispa (Aiton) H.J.P.Winkl.; > Alnus crispa (Aiton) Pursh var. crispa – F; > Alnus crispa (Aiton) Pursh var. mollis Fernald – F; > Alnus mitchelliana M.A.Curtis ex Gray – Gray (1842), not validly published

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Wetland Indicator Status:

• Eastern Mountains and Piedmont: FAC (name change)
• Great Plains: FAC (name change)
• Midwest: FAC (name change)
• Northcentral & Northeast: FAC (name change)

Heliophily: 8