Rumex aquaticus aka Water Dock

Rumex aquaticus belongs to the knotweed family, Polygonaceae. It is a perennial, which means it lives for years. Its common names include red dock and western dock. It is native to the temperate parts of Eurasia. Records span northern and central Europe and much of Asia. They include Russia, China and Japan. They also include Mongolia, Kazakhstan and Kyrgyzstan. The RHS lists Britain and Ireland as native lands too. It grows to about 6 feet [1.8 metres] tall. Kew classes it as a perennial or helophyte, a marsh plant.

It grows in shallow water at the edges of swamps. Records also place it in wet fields, meadows and ditches. These sites show its need for wet soil around its roots. In gardens, it suits pond edges and bog gardens. It can grow in wet soil or shallow standing water. It accepts sand, loam and heavy clay. The soil can be mildly acid to mildly alkaline. It grows in full sun or part shade. The sources give no frost limit or hardiness zone.

Flowers appear from July to August. Each flower has both male and female organs. Wind moves pollen from flower to flower. The evidence gives no flower colour for this species. It gives no fruit details either. Nor does it describe the leaves or stems in detail. Growers can raise plants from seed or split them. Sow seed where plants will grow, in spring or autumn. Split plants in spring once they have taken hold. PFAF does not flag this species as a weed. The accounts name no specific pests or diseases.

PFAF lists cooked leaves as food but rates their food value low. Its safety warning means the amount eaten matters. The plant can hold high levels of oxalic acid. Large amounts may leave the body less calcium to use. Cooking cuts oxalic acid levels but does not remove the warning. People with kidney stones, gout or arthritis should take care. The warning also covers rheumatism and excess stomach acid.

PFAF lists past uses of the root as medicine. People took it as a remedy and used it on skin complaints. Root compounds can act as a laxative or an astringent. Their balance shifts with the dose and time of harvest. These past uses do not prove that treatment is safe. Records also note the use of dried, powdered root to clean teeth.