Catabrosa aquatica aka Water Whorl Grass

Catabrosa aquatica is a grass in the Poaceae family. It is perennial, which means it lives for several years. Its names include whorl grass and waterhair. It grows in temperate, or mild, parts of the Northern Hemisphere. Its native range also reaches southern Chile and southern Argentina. The RHS confirms it is native to Britain and Ireland. Records also place it in Europe, northern Africa, and western Asia. Plants For A Future also lists Greenland and Alaska.

This grass grows about 2.3 feet [0.7 metres] tall. It lives in wet ground and at the water’s edge. In Britain, it grows in shallow streams and drainage ditches. It also grows at the muddy edges of ponds. Other sites include wet, sandy ground near the coast. These records suit water edges, not dry borders. The accounts give no details of leaf or stem form.

Plants For A Future lists flowers from June through August. Each flower has both male and female parts. Wind moves pollen from one flower to the next. Seeds ripen from July through September. Their very small size makes them hard to gather and handle. The sources give no more details of flower or seed form.

Wet soil or shallow water suits its needs on record. Plants For A Future lists sand, loam, and clay soils. It lists mildly acid, neutral, and mildly alkaline soils too. The plant can grow in sun or part shade. Its growing notes are tentative, based on its wild sites. The same source lists USDA hardiness zones 3–7. It suggests ponds and bog gardens as places to grow it. To raise plants, sow seed on the soil’s surface in spring. Keep the seed pot standing in shallow water. Move young plants to their own pots when large enough to handle. Plant them out in summer, or split well-grown plants in spring.

Plants For A Future gives the seeds a low food-use rating. It lists them as edible, with few firm details on their prep. The source reports no known hazards. This does not mean the plant is safe in all cases. It records past use of a decoction as a tonic and stimulant. A decoction is a liquid made by boiling the plant. That report does not show the treatment works or is safe. Records also note that people burn the plant as incense. The source does not flag it as weedy. The evidence gives no facts on specific pests or diseases.