| Family | Scientific Name | Common Name | Habitat | Distribution | Image |
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| Betulaceae | Alnus crispa | Green Alder, Mountain Alder | 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. | 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). | 
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| Betulaceae | Alnus glutinosa | Black Alder, European Alder | Disturbed areas, suburban woodlands, wetland restoration areas (where sometimes planted and spreading). | Native of Europe. Sometimes cultivated, especially northward, and naturalizing in wetlands southwards at least to e. TN and w. NC. Also been reported for Morgan County, TN (Chester, Wofford, & Kral 1997). Reported as well-established in Washington County VA (Virginia Botanical Associates 2018). | 
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| Betulaceae | Alnus maritima ssp. georgiensis | Georgia Alder | Standing water of Ridge-and-Valley spring run. | Endemic to a single site in Bartow County, GA. | 
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| Betulaceae | Alnus maritima ssp. maritima | Seaside Alder, Delmarva Alder | Ecotones between fresh tidal marshes and tidal swamps, open-canopy Atlantic white cedar swamps, streambanks, ponds, shores. | Endemic to five counties in the Delmarva Peninsula of MD and DE. | 
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| Betulaceae | Alnus maritima ssp. oklahomensis | Oklahoma Alder | | Endemic to Johnston and Pontotoc counties, sc. OK. | 
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| Betulaceae | Alnus rugosa | Speckled Alder | Swamps, wet thickets, marshes, alluvial shores, other seepy or saturated wetlands; braided streamhead seepage swamps (in VA). | NL west to SK, south to e. MD, w. VA, WV, IN, n. IL, ne. IA, MN, and e. ND. | 
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| Betulaceae | Alnus serrulata | Tag Alder, Smooth Alder, Hazel Alder | Streambanks, bogs, wet thickets, pondshores, lakeshores. | NS west to s. QC, MO, and OK, south to ne. FL, Panhandle FL, and TX. | 
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