Marsh Arrowgrass

Triglochin palustris

This perennial plant produces striking flowers in summer.


Marsh Arrowgrass has grass-like leaves and striking green-purple flowers. This species reaches up to 50cm tall, growing up from its rhizomes and dense fibrous roots. The leaves of Marsh Arrowgrass rise from a basal sheath, are 2mm wide, deeply-grooved, and have a short, blunt ligule. The flowers occur on a raceme-like spike and are a distinctive green-purple colour with six elliptic tepals crowned by fluffy white stamens. The best time to see Marsh Arrowgrass flowering is in June and July, with each spike holding over 30 flowers.


Marsh Arrowgrass is found in wet meadows, fens, stream banks, and damp grasslands where the soils are calcareous.

Distribution and threats

Marsh Arrowgrass is widespread across Great Britain and is listed as Least Concern for the Red Data book for GB. However, in England, this species is declining and is now listed as Near Threatened due to the loss of its preferred habitats through drainage, agricultural intensification, and lack of grazing. Marsh Arrowgrass is also listed as a rare plant within Oxfordshire and in the last decade, has only been found at a few sites within the county.