Najas flexilis aka Naiad

Najas flexilis, or nodding waternymph, is a small annual water plant. It belongs to the Hydrocharitaceae family. Its native range spans temperate parts of the Northern Hemisphere. This includes much of North America and parts of Europe. In North America, it occurs across Canada and the United States. Its European range includes Britain, Ireland, Scandinavia, and central Europe. The RHS confirms that it is native to Britain and Ireland.

The plant grows to about 1 foot [0.3 metres] tall. Its annual life cycle sets it apart from perennial pond plants. It grows in lakes and rivers, in shallow water. It can live in fresh water or slightly salty water. In America, its habitats extend from sea level into upland areas. Records reach elevations of about 4,920 feet [1,500 metres]. Its small size suits its listed use as a pond plant.

Flowers appear from August to September. Each flower is either male or female. Both kinds of flower grow on the same plant. Water carries the pollen, rather than wind or insects. This makes water part of its breeding process, not just its habitat. The supplied account gives no details of flower colour or fruit. It also gives no leaf or stem features for identification.

For cultivation, provide shallow water rather than a moist garden bed. The plant accepts sandy, loamy, and clay soils beneath the water. It tolerates mildly acid, neutral, and mildly alkaline conditions. It can also grow where the soil contains salt. Full sun and partial shade both suit it. PFAF lists USDA hardiness zones 4–8. Its suggested seed method has not been confirmed for this species. That source proposes sowing ripe seed where the plant will grow. Alternatively, it suggests cool storage in water before spring sowing.

PFAF lists the leaves as edible and describes eating young shoots. These can be eaten raw or cooked, much like watercress. It gives the plant an edibility score of two out of five. It reports no known hazards, but offers no detailed safety assessment. No medicinal use is recorded in that source. Other recorded uses include packing goods in crates and making fertilizer. PFAF does not flag the plant as a weed. The supplied sources give no specific pest or disease information.