Water Sedge

Water Sedge, courtesy of Hurd, Shaw, Mastrogiuseppe, Smithman, and Goodrich.  Plants.usda.gov

Photo courtesy of USDA-NRCS PLANTS Database / Hurd, E.G., N.L. Shaw, J. Mastrogiuseppe, L.C. Smithman, and S. Goodrich. 1998. Field guide to Intermountain sedges. General Technical Report RMS-GTR-10. USDA Forest Service, RMRS, Ogden.  http://plants.usda.gov

Common Name(s):

Water sedge

Scientific Name:

Carex aquatilis Wahlenb.

Scientific Name Synonym(s):

Carex variabilis Bailey
Carex substricta (Kukenth) Mack.
Carex stans Drej.
Carex interimus Maguire




Life Span: Perennial
Origin: Native
Season: Cool


Growth Characteristics: Water sedge is an Obligate Wetland (occurs almost always under natural conditions in wetlands) plant. It is a long lived perennial that grows 8-20 inches tall. It regenerates primarily through the spreading of underground long and short rhizomes that are coarse, scaly, and brown. Long and short rhizomes take part in vegetative reproduction. The long rhizomes branch to produce another plant. The short rhizomes produce more water sedge in tufts or "tiller clumps" The roots live two to three times longer than the shoots. The rhizomes of water sedge grow approximately 2.1 inches (5.3 cm) below the soil surface and form dense clumps. The dense rhizome network results in a tiller density of 11,000 to 22,000 shoots per square foot (1,000-2,000 shoots/m sq). This dense sod stabilizes soils and streambanks. Seed germination rates vary between 20 and 60 percent. Seedlings are most common on drier sites andnd on burned sites.   Water sedge flowers May-August, depending on elevation. 

Seedhead:  The seedhead is a spike, having 3-7 spikelets, 1-3 terminal male spikes and 2-3 lateral female spikes. The male spikes are1/2 inch long, and 1/16-1/8 inch wide. The female spikes, locate on the lower part of the seedhead, are larger than the male, measuring 3/8-1 ½ inches long, 1/8-3/16 inch wide. The female spikes have reddish-brown to purplish-black scales with a paler midrib that is often white-tipped. The seed an achene, yellow to brownish black. Each year approximately 6 to 9 percent of the shoots flower, and few viable seeds are produced. Pollination occurs by wind. 


Leaves: Leaf blades have a waxy appearance at the tips, and are as long as, or a little shorter than, the stem, and found on the lower half of stem. Their width is 1/16-1/4 inch. The color of the leaves is light green to glaucous-green. Each plant produces 8-15 leaves per year.

Stem: The stem is smooth, bluntly to sharply angled (usually triangle-shaped). Stems are found solitary or few together.  

Ecological Adaptations:

Water sedge is found in areas of shallow water or immediately adjacent to water. These include swamps, wet meadows, pond or lake shores, streams, old riverbanks, floodplains, fens or marshes, silted-in beaver ponds, or any other low-lying area with restricted water drainage. The water regime best suited for water sedge is one with the water table above ground level in early June and adequate moisture in the root zone throughout the year. Water sedge grows best on flat or concave surfaces with a maximum slope of 10 percent.   In Utah, it is often found in riparian or wetland habitats at elevations from 8000-11000 feet (2,963 to 4,074 meters). Where water sedge does occur it is usually the dominant or codominant species. Water sedge is a strong competitor and will invade disturbed sites.


Soils: Water sedge usually grows in soils belonging to one of three taxonomic soil orders: Histosol, Inceptisol (cryaquepts), or Mollisol (cruaquoll). It grows best in cold soils with textures ranging from sandy loam to clay. The soil climate can vary from semiarid to humid. The soil reactions are slightly acidic, with a soil pH range of 6.2 to 7.1. The organic matter is mainly composed of massive roots and rhizomes, in varying degrees of decomposition. Water sedge will also grow on mineral soils. It appears that phosphorous is the limiting element of water sedge in wet meadows and correlates with soil temperature in tiller height and number of leaves.

Associated Species: Species commonly associated with water sedge include  willows, sedges, tufted hairgrass, baltic rush, bog birch, leafy aster, spike rush, narrowleaf cottonsedge, reedgrasses, and other species typical of riparian areas.

Uses and Management:

Water sedge is grazed by many ungulates, including moose, and elk, but it is not a major component of their diet. Due to the swampy habitat of water sedge, grazing by most ungulates is limited. Domestic livestock do not readily graze water sedge areas until the soil surface dries in late summer. Water sedge is resistant to grazing, but livestock use in wet areas often results in hummocking and pitting of soils. Production in areas dominated by water sedge is high. It is high in nutrition and also has high protein content. The seeds are utilized by waterfowl. This is an important plant for soil stabilization especially near streambanks. Overhanging sod formed by water sedge on streambanks provides shade and cover for fish. Phosphorus plays a role in productivity and water sedge responds well to phosphorous fertilizer. 
Water sedge habitat provides cover for some birds, waterfowl, and small mammals. Some particular birds associated these habitats include the green-winged teal, the sandhill crane, the common snipe, the common yellowthroat, the red-winged blackbird, and the song sparrow. 


Water sedge's potential for erosion control has been rated as medium, as has its potential for short- and long-term revegetation. Natural succession at disturbed sites, including firelines, and burned and overgrazed areas, occurs rapidly, and sowing exotic grasses is likely to interfere with, rather than promote, native plant establishment. The only exception to this would be where surface erosion is severe. When packstock and hiker use occurs on wet soil, formation of ruts can be severe. New trails should be built on adjacent uplands.