Water grass is grass which thrives in an aquatic environment. Some grasses are truly aquatic grasses, preferring to grow in water and to be primarily submerged in water, while others like soggy ground or shallow waters, and can tolerate dry soil. Water grasses can be found all over the world, with a number of grass species surviving well in water. The rushes are a particularly notable example of water grasses.

Some people like to grow water grass as an ornamental if they have water features. Grasses can dramatically change the look of a pool, pond, stream, or similar feature, adding color and texture to the landscape. They can also be used to reduce the risk of flooding, as water grass will help control water levels. Many of these grasses provide habitat for animals and birds. A water grass planting may attract waterfowl to a garden, just as natural water grasses in wetlands and marshy areas are an important part of the ecosystem.

Water grasses can also be grown for commercial use, ranging from animal fodder to flood control. Historically, water grasses have been used for crafts like basket weaving and in furniture making, and they are also utilized to make ornamental crafts. Habitat restoration in wet areas also classically includes the establishment of native water grasses to restore balance to the area. In addition to being established by people, of course, water grasses famously grow wild in the natural environment.

In some cases, water grass can become invasive. An introduced species may choke out natives, reducing biodiversity and threatening the balance of the environment. Some non native species can actively discourage aquatic organisms from settling, which will drive water birds away, and others become a commercial hassle, becoming entangled in aquatic equipment like boats. Concerns about invasive species have led many gardening organizations to recommend that gardeners work with native species when they want to plant ornamental water grass, to avoid spreading non natives.

Watergrasses come in all styles and colors. Some have long, upright stems which stand up above the water, while others develop a trailing growth habit, floating on the surface of the water. The grass may be green, blue, or yellowish in color, and some flower and produce seeds at various points in the year. Water grasses can be propagated through seeds, cuttings, and divided root clumps. Gardeners who want to establish water grass can explore the options at a local nursery. Staffers may have specific recommendations for customers, along with tips on managing invasive water grass species.