Juncus arcticus var. mexicanus
Brittonia 35: 308. 1983.
Herbs, 2–8 dm. Culms usually compressed. Leaves: blade distinct, somewhat flattened, to 20 cm or more. Flowers: tepals usually brown or blackish, 3.5–4.5(–5.5) mm; filaments 0.2–0.4 mm, anthers 1.2–2.2 mm.
Habitat: Intermittent or permanent water courses, around springs, and in meadows in sandy or gravelly soils
Elevation: 500–3200 m
Ariz., Calif., Colo., N.Mex., Nev., Utah, Mexico, Central America, South America.
Juncus arcticus var. mexicanus is the common phase of the species in the extreme southwest United States and Mexico; northward the variety becomes sporadic in its occurrence. Rare individuals having leaves with blades are sometimes found in otherwise bladeless populations in more northern areas but it is doubtful that these oddities represent an equivalent variant.