Carex hartmanii Caj., a sedge new for the Netherlands, was discovered on Terschelling, one of the Frisian Islands. It grows there abundantly in a marshy dune valley west of the Boschplaat. The species is closely allied to C. buxbaumii Wahlenb., from which it mainly differs by the cylindrical, not club-shaped terminal spikelet, the shorter lowest bract, and the distinctly nerved, smaller utricles.