Najas marina

Najas marina is a highly variable aquatic plant of fresh and brackish water found almost worldwide, occurring above all in large lakes; in Central and South America it is found only sporadically.¹ Its stems, up to approx. 1 m long, branch only sparingly and are densely spiny in some plants, smooth in others.¹ The narrow, rigid leaves break easily, appear to be arranged in pairs or in whorls and usually bear several spines along the margin.¹ The dioecious plants vary so greatly in their seeds, leaf dimensions and spininess that many varieties have been established.¹

In Germany the species is considered endangered; plants of native origin are sometimes cultivated in garden ponds.¹ As an aquarium plant it is listed for the midground and background, but one specialist author's attempts to cultivate plants from Mexico and Malawi failed.¹