Vallisneria spiralis aka Coiled Vallisneria

Vallisneria spiralis belongs to the Hydrocharitaceae family. It is a water plant that lives for years and stays green. Its common names include tape grass, eel grass, and water celery. Its native range runs from Europe to Indo-China and southern Africa. It is not native to Britain or Ireland. It grows in still water and in water that flows. In Britain, records include ponds that warm water from mills feeds.

The leaves stay green all year. They can grow to 3.3 feet [1 metre] long. This does not tell us the plant's full height or spread. The plant grows runners that form roots. Growers can split these to make new plants. Its long leaves suit a large aquarium or deep outdoor water. It also grows as a pond plant and adds oxygen to water. The sources give no facts about bark or fruit.

Flowers appear from June to October. Each plant bears male flowers or female flowers, not both. Both sexes must grow together to make seed. Male flowers form below the water. Female flowers sit on the surface. The male flowers break free and float up. They drift into a small hollow that a female flower makes. This brings the flowers together so they can form seed. Water moves the pollen, and the plant cannot use its own pollen to form seed.

Grow this species in sun, not shade. It likes soil with a slight acid level. It can also grow in neutral soil or soil with a mild alkaline level. Sand, loam, and clay can all support it under water. It needs to grow in water, not just damp ground. PFAF lists USDA zones 7–10. But it warns that the plant has limited hardiness in Britain. Only the mildest parts there suit outdoor growth best. Split rooted runners in the growing season to make new plants. PFAF suggests that seedlings spend their first winter under glass. Plant them outdoors once the last expected frosts have passed.

PFAF says people can eat the young leaves raw. It gives the plant a low food-use score: one out of five. It also notes use in folk medicine. These uses include remedies for poor appetite and stomach complaints. Such reports do not prove that these uses work or are safe. PFAF lists no known hazards. But it gives no clear evidence of safety for pets. It lists the species as having no weed potential. The supplied sources name no pests or diseases. Nor do they give advice on how to treat such problems.