Asiatic Sand Sedge (Carex kobomugi)
Photo credit: Zach Bradford, https://flic.kr/p/nARPfx

Asiatic Sand Sedge

(Carex kobomugi)

Species at a Glance

Asiatic sand sedge, also called Japanese sedge, is a course, stout, perennial sedge that grows 10-30 cm (4-12 in) in height and is adapted to coastal beaches and dunes. It forms extensive colonies through cord-like rhizomes that extend many feet under the sand and produce new shoots.

Identification

Leaves: Young leaves are yellow-green in color, stiff, and rough to the touch along the edges. Older basal leaves are somewhat wider, darker green in color, and leathery to the touch. The edges are serrated, which can be seen with the help of a hand lens. Leaves are 3-6 mm wide and are often longer than the triangular stems.

 

 

Flowers: Individual plants have either male or female flowers that are arranged in dense clusters or “spikes” at the end of a flowering stalk. Male flower spikes are cylindrical in shape and measure 3-4 cm long. Female flower spikes are more slender and typically longer measuring 3-6 cm. Flowering occurs from April to June.

Fruit/Seeds: A papery sac called a perigynium encloses the female flowers, each of which develops into a single-seeded fruit called an achene.

 

Stems/Roots: The base of the triangular stems is covered in brown scales.

Similar Species

Asiatic sand sedge resembles American beach grass (Ammophila breviligulata), and beach panic grass (Panicum amarum). Leaves of Asiatic sand sedge are longer and more tapered than the look-a-like grasses, have a yellow-green rather than bluish-green cast, and small teeth along the margin.

Habitat

Asiatic sand sedge grows on dunes and on the upper parts of ocean beach wash flats that have recently been disturbed by ocean storms. Like American beach grass, it appears to create more habitat for itself by trapping wind-blown sand to form dunes. Sand burial appears to stimulate the growth of rhizomes.

Spread

Soon after the plant was discovered in the United States, Asiatic sand sedge was observed to be potentially useful for stabilizing sand dunes, and thus was planted intentionally on dunes in New Jersey and other beaches on the east coast. This plant likely made its way to New England through either intentional planting or the water dispersal of plant fragments or seeds. While it does produce seeds, germination rates are low and primary spread from this species occurs through an extensive rhizome system.

Distribution

Native to coastal Japan, China, and Korea, Asiatic sand sedge was first reported in the United States in New Jersey in 1929. It was thought that it washed ashore from shipwrecks that were carrying oriental porcelain and using Asiatic sand sedge as a packing material. It can now be found down the east coast from Massachusetts to North Carolina, and also in Oregon.

 

Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.

Environmental Impacts

Asiatic sand sedge has the ability to form dense stands on coastal dunes. It has been found in densities of up to 200 plants per square meter. This density effectively excludes native beach grasses and makes dunes more susceptible to being blown out.

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