Publication: Preslia. 47: 107. 1975.
selected vouchers: WTU
Notes: FNA2: "The branchlet leaves of Diphasiastrum alpinum are unique in the genus, and the trowel-shaped underside leaves with their flared and rolled blades and contracted bases are particularly unusual. The leaves of the other North American species are much simpler in shape and contour." Diphasiastrum alpinum hybridizes with Diphasiastrum sitchense; hybrids are not uncommon in the Cascades of Washington where the parent species co-occur, and can be distinguished by their intermediate morphology.