- Name also: Curly Dock, Yellow Dock, Sour Dock, Narrow Dock, Narrow-leaved Dock, Garden Patience
- Family: Dock Family – Polygonaceae
- Growing form: Perennial herb.
- Height: 40–120 cm (15–50 in.). Stem often reddish, unbranched up to inflorescence, erect through winter.
- Flower: Regular, small, ca. 3 mm (0.12 in.) wide. Usually bisexual. Perianth segments in two whorls of three. Segments of outer whorl small and turned backwards or spreading. Inner whorl forms the fruit valves which are rounded-triangular, somewhat heart-shaped, and with more or less entire margins. The segments usually have a prominent pimple on the midrib. 6 stamens. Pistil consists of 3 fused carpels, styles 3. Joint on flower stalk (ca. 1 cm, 0.4 in. long) near base. Flowers in clusters forming racemes.
- Leaves: Spirally. Basal leaves almost like in rosette, long-stalked. Upper leaves shorter-stalked. Blade rough on both sides, 4 to 5 times as long as broad, elongated lanceolate with rounded or tapered base and strongly wavy margins (rarely almost waveless).
- Fruit: Reddish-brown, sharply three-edged, glossy achene, 2.5 mm (0.1 in.) long.
- Habitats: Shores, fields, waste ground, roadsides.
- Flowering time: July–August.
Genus Rumex is taxonomically difficult as the species hybridise frequently – curled dock especially with northern dock (R. longifolius) and broad-leaved dock (R. obtusifolius). The valves enclosing the ripe fruit are often essential to identification.
Curled dock is a perennial herb. It belongs to an intrageneric section in which the flowers are bisexual and the fruit valves are clearly longer than the fruit. This species often grows on seashores along seaweed heaps and on bird rocks where there is plenty of nitrogen available. Water is its main agent of dispersal. The pimples on the fruit valves are deemed to function as floats. Sometimes waves also move detached seedlings, which re-establish when stranded. Curled dock individuals that flower late in the autumn may seed on the snow as they stay erect due to their rigid stem.