Glyceria fluitans aka Floating Manna Grass

Glyceria fluitans is a perennial grass in the Poaceae family. Its common names include floating sweet grass and manna grass. Its native range spans Europe to Turkmenistan and includes Morocco. The RHS also records it as native to Britain and Ireland. Kew places it in temperate regions and lists a wetland growth form. It suits wet ground rather than a dry garden bed.

Plants For A Future gives a height of 5 feet [1.5 metres]. It lists a spread of about 3 feet [0.9 metres]. This grass grows in wet places and shallow water. Pond edges and bog gardens provide suitable sites for it. It can also form part of a wetland planting. Its value there includes cover and food for wildlife. Seed and division offer two ways to raise more plants. Natural spread through rhizomes can also help it occupy wet ground.

The flowers contain both male and female organs. Wind carries the pollen between flowers. The supplied species evidence gives no firm flowering season. For growing conditions, the soil must stay moist or wet. The plant can also grow with its roots in water. It accepts sandy soil, loam, and clay. Mildly acid, neutral, and mildly alkaline soils all suit it. It grows in sun or partial shade. Plants For A Future lists USDA hardiness zones 2–8. Its UK zone number does not use the RHS H-rating scale.

The mature grain is the edible part listed for this plant. Plants For A Future gives it a moderate food rating. Clean grain can be cooked as porridge or ground into meal. Toasting offers another way to prepare the seeds. This food use does not establish that leaves are safe. Do not treat the foliage as a leafy vegetable. The source warns against extending grain use to green shoots.

Seed quality and water quality matter when gathering grain. Reject grain that smells bad or shows mould or discoloration. Discard seed heads with hard, dark fungal growths replacing grains. The source flags ergot among possible wetland grass hazards. Avoid harvest sites exposed to sewage or polluted runoff. Plants For A Future also flags weed potential. Consider its spread when choosing a place beside a pond.