Equisetum fluviatile aka River Horsetail

Equisetum fluviatile is in the horsetail family, Equisetaceae. People call it swamp horsetail and smooth horsetail. It lives for years and forms upright clumps. These grow from rhizomes, which are stems below ground. It is native across the temperate Northern Hemisphere. Its native range includes Britain and Ireland. It grows in shallow lakes, ponds, and ditches. These wet homes guide its use in gardens.

Garden plants reach about 1.6–3.3 feet [0.5–1 metre] in height and spread. Clumps take two to five years to reach full size. The stems stand upright and have ridges and joints. They are hollow through most of their insides. Yellow-brown bands mark the outside of the stems. Thin branches form whorls, or rings, at the stem nodes. The plant keeps some leaves through the winter. Fertile stems bear blunt cones at their tips. These cones make spores, not flowers or fruit.

Give this horsetail rich soil that stays moist all year. It also grows in water 0.33 feet [0.1 metre] deep. Full sun and part shade both suit it. It grows in chalk, clay, loam, and sand. It accepts acid, neutral, and alkaline soils alike. The RHS gives it a cold hardiness rating of H7. This covers harsh winters in continental Europe below −20°C. Choose a site that can meet its need for moisture.

Its upright shape suits ponds, bog gardens, and wet containers. A pot also helps keep its spreading rhizomes in bounds. Pots thus help where plants have little room to spread. Divide clumps in spring to make new plants. Cut out dead or damaged stems to keep plants tidy. The RHS reports few usual pest or disease problems. Plan for its water needs and room to spread.

Plants For A Future lists some parts as edible. These are cooked roots and fertile spring shoots. The roots hold starch, but shoots have little food value. Read these food records with the plant's risks in mind. The plant contains thiaminase, so large amounts can cause serious harm. This enzyme can reduce the body's store of B vitamins. The source says heat or thorough drying destroys the enzyme. This does not make unrestricted use safe. It also records past use of barren stems to curb bleeding. This does not mean you should use them for home treatment.