Platanthera tescamnis

"This species is distinguished by a small column with short rostellum lobes that position the viscidia above the orifice of the spur. The species exhibits ecological preferences that are unique in the Limnorchis group, occurring at relatively low elevations and in comparatively dry habitats in a hot, arid region." (Sheviak and Jennings 2006). The authors explain that Platanthera tescamnis is distinct from P. sparsiflora and what has been called P. ensifolia or P. sparsiflora var. ensifolia, saying, "Platanthera sparsiflora is a variable species to which Limnorchis ensifolia and L. laxiflora have been referred. Recently, authors have adopted L. ensifolia for a group of plants that have also been referred to L. laxiflora and P. sparsiflora. None of these existing names apply to a recently delineated but related group," which they describe as Platanthera tescamnis. Further, they say, "Jennings (1985, 1987, 1988, 1991a, 1991b, 1996) adopted Platanthera sparsiflora var. ensifolia (Rydb.) Luer, and Weber (1990) Limnorchis ensifolia, for the Colorado representatives of P. tescamnis. The holotype of L. ensifolia [Arizona: Mt. Humphrey, 8600 ft., 31 Jul 1897, R.E. Kunze s.n. (NY 8998)] from the San Francisco Peaks north of Flagstaff, Arizona, however, is clearly referable to P. sparsiflora, as previously determined by Ames (1910) and Correll (1950)."

Platanthera tescamnis is a recently-described orchid occurring in mesic soils of riparian areas, alluvial meadows, open coniferous forests, and (rarely) emerging from shallow waters of streams, fens, and seeps of the Great Basin and Colorado Plateau ecoregions in Colorado, Utah, and Nevada, and California. It also historically occurred in Arizona and is potentially extirpated from the state, though field surveys are needed to confirm this. There are an estimated 94 occurrences rangewide, which are threatened by drought and climate change, cattle grazing, and recreational activities.

Platanthera tescamnis occurs in western North America, within the Great Basin and Colorado Plateau ecoregions of the United States in Colorado, Arizona, Utah, and Nevada, and California (Sheviak and Jennings 2006, NAOCC 2024). The record from Arizona is from a historical herbarium collection from Middle Mesa in Apache County collected in 1916 (C.T. Vorhies s.n. (ARIZ))(SEINet 2024). The Arizona Natural Heritage Program considers this species to be historical (AZNHP 2013); however, a photo-based observation was made in 2022 in Apache-Sitgreaves National Forest, which needs confirmation (iNaturalist 2024). Range extent was estimated using herbarium specimens and photo-based observations documented between 1993 and 2024 (CCH2 2024, GBIF 2024, iNaturalist 2024, SEINet 2024).

By applying a 1 km separation distance to herbarium records and photo-based observations documented between 1993 and 2024, there are estimated to be 94 occurrences rangewide (GBIF 2024, iNaturalist 2024, SEINet 2024). The Colorado Natural Heritage Program tracks 38 occurrences, though there are likely more than this if voucher data from herbarium specimens is included (CNHP 2010).

Specific threats to Platanthera tescamnis across its range are currently unknown. However, this species is commonly found in mesic soils at the edges of riparian habitat, and (less frequently) in shallow water at the edges of streams, fens, and seeps; though it is generally found in drier habitat and at higher elevations than those occupied by the closely related P. sparsiflora (Sheviak and Jennings 2006). Climate change and drought are a potential concern for Platanthera tescamnis, given that the Colorado Plateau is predicted to become hotter and annual precipitation is predicted to decrease by 6% by the end of the century (Garfin et al. 2010). The Great Basin region is also predicted to become more arid, with more frequent and longer-lasting drought conditions (Snyder et al. 2018). In Colorado, cattle grazing was listed as a threat for two occurrences, and one occurrence listed recreational activities as a potential threat (CNHP 2010).