Rumex obtusifolius aka Broad Leaved Dock

Rumex obtusifolius is broad-leaved dock, also called bitter dock. It belongs to the knotweed family, Polygonaceae. Its native range covers northern and western Europe, including Britain and Ireland. It also extends from Algeria to Tunisia in North Africa. This perennial grows in fields, rough ground, grassland, and marshy places. It also grows along hedges and field edges.

A strong taproot supports its upright growth. In gardens, it reaches 3.3–4.9 feet [1–1.5 metres] tall. Its spread reaches 1.6–3.3 feet [0.5–1 metre]. Plants take two to five years to reach full size. Smooth, oblong leaves grow on long stalks. The plant loses its leaves as the season ends. Upright flower sprays carry small green and red blooms. The fruit starts in similar shades, then turns rusty brown. Stems turn brown too, and may remain through winter.

Grow this dock in full sun or partial shade. It accepts sand, loam, clay, and chalk soils. Acid, neutral, and alkaline ground all suit it. It prefers moist soil but accepts a range of drainage conditions. Plants grow in both sheltered and exposed sites. The RHS gives it an H7 hardiness rating. Plants For A Future lists USDA zones 4–8. Its tolerance suits rough garden edges and wildflower meadows. It also provides food for wildlife.

Broad-leaved dock can become a stubborn weed in farm soils. It spreads freely from seed, while pieces of root can regrow. Remove unwanted plants while they are young and easier to lift. Cut flower stems before seeds form to limit further spread. Slugs and aphids may attack it. Disease causes few problems, according to the RHS. These traits matter when choosing a place in a garden. Wildlife value does not remove the need to control its spread.

Young leaves and stems have recorded uses as cooked food. People also eat the seeds raw or cooked. Ground seeds can join cereal flour, though gathering them takes work. Leaves taste bitter, with early spring growth offering milder flavour. Oxalic acid makes large servings unsafe for people and pets. Cooking lowers the acid content but does not remove every concern. People prone to kidney stones, gout, or arthritis need extra caution. Traditional remedies use the leaves and roots; these are not proven treatments. The roots also yield yellow, green, brown, and grey dyes.