Juncus ranarius; The Frog Rush is a small annual rush which usually forms prostrate rosettes. This is very characteristic. Single stems grow up too no more than 5 cm or so. It can be found world wide in the sub-arctic zone of the northern hemisphere reaching more south into the moderate climate regions where it is more or less restricted to brackish environments. On Iceland it has a scattered distribution but is nevertheless quite common. It prefers open soils (moist soils). Quite characteristic are the shape of the perianth leaves of the flowers: the outer three are distinctly longer than the inner three. Both have membranous margins. The official name though not clear. Outside Iceland the species is often named as Juncus ambiguus and in the past it has been named J. bufonius ssp. ambiguus or K. bufonius ssp. ranarius.
It is a member of the rush family (Juncaceae).