Triglochin palustris; The Marsh arrowgrass is a slender monocotyledon species that grows commonly on all wet soils on Iceland except for the highland regions and dry sand plains of the south coast. A close relative is Triglochin maritima (Sea Arrowgrass) which grows on saline soils along the sea. This species has a flower stem far more densely occupied with flowers. Another difference is the elongated fruits of the Marsh Arrowgrass compared to the shorter and thicker fruits of the Sea Arrowgrass. Both species spread a sour odour when leaves are torn or shredded.
It is a member of the Arrowgrass family family (Juncaginaceae). The Icelandic name of this species is Mýrasauðlaukur.