Triglochin maritima

Triglochin maritima is a species of flowering plant in the arrowgrass family Juncaginaceae. It is found in brackish marshes, freshwater marshes, wet sandy beaches, fens, damp grassland and bogs. It has a circumboreal distribution, occurring throughout the northern Northern Hemisphere. In the British Isles it is common on the coast, but very rare inland.

Description
It is similar to marsh arrowgrass (Triglochin palustris) but has the following differences: it has stolons, is stouter. The leaves are fleshy and not furrowed above. It is not very aromatic. The raceme is more dense and like sea plantain. The flowers are fleshier. The fruits are oval, 4 mm long, 2 mm wide.

It varies in height from 8-30 in. It flowers in May to August; flowers are greenish, 3 petalled, edged with purple, 1/8 in across, in a long spike. Common names include seaside arrowgrass, common arrowgrass, sea arrowgrass and shore arrowgrass.

It can be an annual or perennial.

Triglochin concinna is a synonym of this species.

This plant is believed to be toxic, as it can produce cyanide. However, this is usually when the plant is distressed in drought conditions or due to over harvesting, usually by grazing animals. There is a common belief that this species has been known to cause losses in cattle, with green leaves being more toxic than dried material, yet sheep and deer graze on the plant, especially in rural seaside areas. It could be that belief in the plants' toxicity is apocryphal and based on anecdotal evidence.