Gray Alder, Mountain Alder, Thinleaf Alder: Alnus incana ssp. tenuifolia (Synonyms: Alnus incana var. occidentalis, Alnus incana var. virescens, Alnus occidentalis, Alnus xpupusii, Alnus rugosa, Alnus rugosa var. occidentalis, Alnus tenuifolia, Alnus tenuifolia var. occidentalis) -
California Alder, White Alder: Alnus rhombifolia (Synonym: Alnus rhombifolia var. bernardina) -
Oregon Alder, Red Alder: Alnus rubra (Synonyms: Alnus oregona, Alnus oregona var. oregona, Alnus oregona var. pinnatisecta, Alnus rubra var. pinnatisecta) -
Siberian Alder: Alnus viridis ssp. fruitcosa (Synonyms: Alnus fruticosa, Alnus viridis var. fruticosa)
Mountain Alder, Sitka Alder, Slide Alder, Wavy-leaved Alder: Alnus viridis ssp. sinuata (Synonyms: Alnus alnobetula, Alnus alnobetula ssp. sinuata, Alnus crispa ssp. laciniata, Alnus crispa ssp. sinuata, Alnus sinuata, Alnus sitchensis, Alnus viridis ssp. fruiticosa, Alnus viridis ssp. sinuata, Alnus viridis var. sinuata, Duschekia sinuata) - This taxon is currently recognized as Alnus alnobetula ssp. sinuata in Oregon.