About Juncus marginatus Rostk.
Juncus marginatus Rostk. is a grass-like, herbaceous, short-lived perennial that grows from short rhizomes. It forms dense tufts or clumps that reach 30 to 130 cm in height, and the species is sometimes rhizomatous. Its leaf blades are flat. Flowers are clustered into a terminal inflorescence called a glomerulus. Each flower has three stamens and three sharply acute, reddish-brown sepals. Seeds develop inside a rounded, beakless capsule. The seeds themselves are small, spindle-shaped, yellow to light brown, around 0.5 mm long, plump and ribbed. They lack a tail, but have sharp points called apiculate tips at each end. The diploid chromosome count for this species is 38. Juncus marginatus is distributed across North America, primarily in the Eastern and Southeastern United States, with its range extending to Texas and South Dakota. It also occurs in Ontario, Canada; California, Colorado, New Mexico, and Oregon in the western United States; Cuba in the West Indies; and Central America. It grows in moist to wet bogs, shorelines, marshes, and ditches, in sandy, peaty, or clayey soils. One historic population was recorded in Minnesota until 1999, when additional small populations were discovered in Anoka County. Due to its rarity in the state, it is listed as an endangered species in Minnesota. In Minnesota, the species grows in shallow wetland prairies of the Anoka Sand Plain, where normally dry sandy ground lies below the water table.
