Triglochin palustris or marsh arrowgrass is a species of flowering plant in the arrowgrass family Juncaginaceae. It is found in damp grassland usually on calcareous soils, fens and meadows. It has a circumboreal distribution, occurring throughout northern parts of the Northern Hemisphere. It can be found locally in the British Isles especially the north.
The leaves are linear, 10 to 20 cm long, rounded on the lower side, deeply grooved on the other.
It has many 3 petalled flowers arranged in a long spike, with purple edged perianth segments, 2mm long. It flowers from June until August.
The fruits are club shaped, 10mm long and 2mm wide.
Triglochin maritimum (Sea arrowgrass) is similar 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 are more dense and like Sea Plantain. The flowers are fleshier. The fruits are oval, 4 mm long, 2 mm wide.
- "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-02-25. Retrieved 2014-10-17.
- "Triglochin palustris". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 15 December 2015.
- Rose, Francis (2006). The Wild Flower Key. Frederick Warne & Co. pp. 486–487. ISBN 978-0-7232-5175-0.
- Sterry, Paul (2006). Complete British Wild Flowers. HarperCollins Publishers Ltd. p. 188. ISBN 978-0-00-781484-8.