Triglochin palustris aka Marsh Arrow Grass

Triglochin palustris, or marsh arrowgrass, belongs to the Juncaginaceae family. It is a perennial that grows from underground rhizomes. Its native range spans subarctic and temperate regions. Records include much of Asia and North America, including Greenland. The RHS also lists it as native to Britain and Ireland. It grows in marshes, often among tall grasses. Its wetland habitat guides its use in gardens.

Marsh arrowgrass reaches about 1.6 feet [0.5 metres] in height. Its growth returns each year from its underground parts. Flowers appear from June to August. Each flower has both male and female organs. Wind carries the pollen, rather than insects. The available sources give no details about fruit shape. They do, however, record uses for the seed. No mature width is given for garden plants.

Choose an open site with sun and wet ground. This plant does not grow in shade. It can grow in shallow water or a bog garden. Pond margins offer another setting for its moisture needs. It accepts sandy, loamy, and clay soils. Soil may be mildly acid, neutral, or mildly alkaline. It can also grow in salty soil. Yet it does not need high salt levels to survive. PFAF lists a USDA hardiness range of zones 4–8.

Spring division provides one way to raise more plants. Large divisions can go straight into their final growing place. Grow small divisions in pots until they establish well. PFAF suggests a greenhouse or cold frame for this stage. Move these plants out in summer or the next spring. Its seed-sowing guidance is tentative, rather than based on species-specific information. The source does not flag the plant as weedy. It lists no known medicinal or other non-food uses.

Food uses need care because green parts can contain toxins. The white leaf-stem base has been eaten raw or cooked. Cooking can release an unpleasant smell, though the stems taste sweet. Seeds have been parched and ground into flour. Roasted seeds have also served as a coffee substitute. These records do not make the whole plant safe to eat. Green leaves may contain a cyanogenic glycoside. Levels pose greater concern during drought and just afterward. Ruminants face a particular risk from this toxin.