Oreojuncus trifidus

This record represents the narrow concept of Oreojuncus trifidus not including O. monanthos (which is only in Europe), following Záveská Drábková and Kirschner (2013). In contrast, O. monanthos (previously named Juncus trifidus var. monanthos) is included in the synonymy of J. trifidus by Kartesz (1994, 1999) and FNA (vol. 22, 2002). The treatment of J. trifidus ssp. carolinianus has been controversial. It was excluded from Záveská Drábková and Kirschner (2013) and treated as a synonym of J. trifidus (= O. trifidus) in Clemants (1990), Knapp in Naczi (2016), and Weakley et al. (2024). Juncus is a paraphyletic genus (Knapp in Naczi 2016, Brožová et al. 2022, Procków and Záveská Drábková 2023). Záveská Drábková and Kirschner (2013) transfer Juncus trifidus to Oreojuncus, which has been retained in Knapp in Naczi (2016), Brožová et al. (2022), and Procków and Záveská Drábková (2023), based on character divergence, including morphology and chromosome numbers, as well as phylogentic position at the base of Juncaceae, sister to the rest of the family.

This taxon is circumboreal, occurring in rocky crevices at high elevations and arctic-alpine habitats in northern Eurasia, northeastern North America, Greenland, Iceland, Canadian arctic islands (Baffin, Nunavut) southeast to North Carolina and Tennessee in the eastern United States. Threats include development, invasive species, and trampling from human recreational activities. Little is known about trends, but with a large range extent and large number of occurrences, this species is considered secure.

This taxon "is circumboreal, occurring in arctic-alpine situations in [northern] Eurasia, [northeastern] North America, Canadian arctic islands (Baffin, Nunavut), Greenland, Iceland. In North America, it ranges from [northern] NL (Newfoundland and Labrador) to [northern Quebec], south to [southern] New England and [New York]; disjunct southwards in [Pennyslvania] (1868 collection with vague locality), [Maryland] (Cumberland Narrows, Alleghany County), [West Virginia] (North Fork Mountain, Pendleton County), [Virginia] (Stony Man, Page County), [Tennessee] (Mount Leconte, Blount County), and [North Carolina] (Craggy Pinnacle, Craggy Dome, and Craggy Gardens, Buncombe County; Eagle Cliff, Mitchell County; Three Top Mountain, Ashe County)" (Weakley and the Southeastern Flora Team 2024).

By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1993 and 2024, it is estimated that there are thousands of occurrences rangewide (GBIF 2024, iNaturalist 2024, NatureServe 2024, SEINet 2024).

This taxon has a limited distribution in the southern Appalachians, making it vulnerable to human disturbance, such as trampling, in this portion of its range (Southern Appalachian Species Viability Project 2002). However, rangewide threats are not widely documented, and it is potentially threatened by development, invasive species, and other threats in some places.