Kalmia polifolia

The epithet 'polifolia' is taken by Voss (Flora of Michigan, vol. 3, 1996) to be the old generic name Polifolia, and not an adjective 'poliifolia' (having leaves like Polium).

Kalmia polifolia is a perennial shrub occurring in swamps, bogs, and on wet alpine slopes in northern North America, from the Northwest Territories east through Newfoundland and Labrador in Canada, south to New Jersey and Pennsylvania and New Jersey, west through Minnesota, and Montana in the United States, and potentially introduced in West Virginia. There are over 1,300 estimated occurrences of this species in its native range, which are threatened by invasive species, alteration of hydrology, succession, logging, rights-of-way construction and maintenance, and likely other threats in some places. This species is closely related to Kalmia microphylla, and taxonomic treatments of the two entities differ. Little is known about threats or trends, but with a large range extent and high number of occurrences, Kalmia polifolia is considered secure.

Kalmia polifolia occurs in northern North America, from the Northwest Territories east through Newfoundland and Labrador, south to New Jersey and Pennsylvania, west through Minnesota in the United States and Canada (FNA 2009, Weakley and the Southeastern Flora Team 2025). It also is disjunct and possibly introduced in West Virginia (Weakley and the Southeastern Flora Team 2025), and is introduced in England (FNA 2009). Reports of Kalmia polifolia (in the strict sense) in Montana are actually based on misidentifications of larger-statured individuals of Kalmia microphylla (Montana Natural Heritage Program 2024). The native range extent was estimated using herbarium specimens and photo-based observations documented between 1994 and 2025 (GBIF 2025, iNaturalist 2025, RARECAT 2025, SEINet 2025).

By applying a 1 km separation distance to herbarium records and photo-based observations documented between 1994 and 2025, there are estimated to be over 1,300 occurrences in its native range (GBIF 2025, iNaturalist 2025, RARECAT 2025, SEINet 2025).

Kalmia polifolia is threatened by invasive species, alteration of hydrology, succession, logging, rights-of-way construction and maintenance, and likely other threats in some places (NatureServe 2025). There is insufficient data, including anecdotal accounts, to understand the scope and severity of threats for this taxon. However, they are considered negligible given the broad range and large number of occurrences of the species and its somewhat flexible and abundant habitat, as well as no obvious intrinsic vulnerabilities.