[2] It also occurs around the four main Japanese islands,[3] and Taiwan,[2] which is the southernmost distribution of the sedge.

[5] It was found in 1929 at Island Beach State Park, New Jersey, where it may have arrived after ships from Japan were wrecked off the American coast.

[6] Its distribution in the United States now extends from Rhode Island to North Carolina.

[6] The biodiversity of native plants is markedly reduced in areas dominated by Carex kobomugi, which has knock-on effects on animals, such as the hairy-necked tiger beetle, Cicindela hirticollis, and the piping plover, Charadrius melodus.

[6] The state governments of Massachusetts and Connecticut have banned the sale and distribution of Carex kobomugi.