Sedge grows well along the Pacific Coast. Slough sedge can be found along the coast from British Columbia south to northern California.
This evergreen sedge is not a grass, but can take the place of a grass in wet and shallow bogs, marshes, and riverbanks. It also does well in meadows, ditches, swamps, and muddy areas.
There is only one sedge in our area. The sedge will grow in salty, marshy, and freshwater areas.
Carex obnupta is often found growing near Skunk cabbage (watch for the large yellow flowers).
Slough sedge is available commercially and easily propagated.
Why this lowly plant is important? It is key to maintaining wetlands functioning. The perennial sedge performs several functions such as:
- Helping to control and maintain stream banks by minimizing erosion and improving stream structure.
- Slowing sediment flow allows the nutrients to settle. This generates a nutrient rich habitat and improves water quality.
- Abating storm water.
- Supporting wetland species.
C. obnupta accomplishes these tasks in several ways.
The horizontal, creeping rhizomes (root-like structures) help anchor the plant. The rhizome shoots can also generate new plants creating new Sedge tufts (or clumps) about a foot wide.
A dense, underwater rhizome network develops as the clumps grow into larger beds or colonies.
The uneven tufted surface provides concealment, nesting, and bedding for many birds and mammals.
The tall (up to four feet) male spikes rise above the shorter female flowers. Additional vegetative stems help conceal nest and bedding areas.
Male flowers spikes typically rise above the female flowers and have yellow pollen at peak bloom time. Female flowers have a white sticky substance for collecting the pollen. Dark, lens-shaped seeds are stratified over the winter.
The fertile and non-fertile stems have different shapes. A cross-section cut of the fertile stems will reveal a triangular shape. Non-fertile, or vegetative stems without flowers have a “W” shape and were harvested for basketmaking.
The process of harvesting helps to move nutrients in that the process of creating more leaves transports nutrients from the rhizomes.
Birds: Several birds take advantage of the foliage for bedding, nesting, and consume sedge seeds. Birds include game and other marsh/shore/song birds).
Wetland mammals: Muskrats, minks, beavers, and otters use the foliage to conceal their travel.
Insects: Several butterflies and moths are supported including:
- Umber Skipper (Poanes melane),
- Common Ringlet (Coenonympha tullia),
- American Ear Moth (Amphipoea americana),
- Dun Skipper (Euphyes vestris),
- Olive Green Cutworm Moth (Dargida procinctus),
- Elachista cucullate, and
- Lesser Wainscot (Mythimna oxygala).
NOTE: Slough sedge is considered invasive in some areas and is very difficult to remove.
–East Multnomah Soil & Water Conservation District (https://emswcd.org/slough-sedge/)
–USDA, Natural Resources Conservation Service, Slough sedge brochure (www.plants.usda.gov/plantguide/pdf/cs_caob3.pdf)
–Univ. of Washington, Bothell (https://www.uwb.edu/wetlands/plants/carex-obnupta)
–California Native Plant Society (https://calscape.org/Carex-obnupta-())