Juncus effusus, with the common names common rush or soft rush, is a perennial herbaceous flowering plant species in the family Juncaceae. In North America, the common name soft rush also refers to Juncus interior.
Juncus effuses, commonly known as soft rush, common rush, bog rush or mat rush, is a grasslike-like, rhizomatous, wetland perennial that features smooth, upright, cylindrical, unjointed, spire-like green stems (leaves are absent) which grow in spreading basal clumps to 20-40” tall. It is one of the true rushes. It has a nearly cosmopolitan distribution, being found in many places around the world, but primarily in cool-temperate regions, particularly ones having wet soils. It is often found growing in ditches, bogs, swamps, marshes, wet pastures, and along the margins of lakes and rivers. Stems are usually solid, with the leaves typically reduced to bladeless basal sheathes. Insignificant, minute, yellowish-green to pale brown flowers bloom in one-sided clusters (many-flowered cymes) located on stem sides slightly below the stem tips. Flowers emerge in summer (July to September). It can be invasive anywhere with moist soil.