- Name also: Broadleaf Dock, Broad Leaved Dock, Bluntleaf Dock, Dock Leaf, Butter Dock, Bitter Dock
- Family: Dock Family – Polygonaceae
- Growing form: Perennial herb.
- Height: 50–130 cm (20–50 in.). Stem basal part almost unbranched, upper branches quite erect.
- Flower: Regular (actinomorphic), approx. 5 mm (0.2 in.) across, bisexual. Perianth-segments in two whorls of three. Segments of outer whorl small and spreading–obliquely forward-pointing. Inner whorl forms fruit valves, which are widely ovately triangular. Stamens 6. Pistil of 3 fused carpels, styles 3. Joint on flower-stalk (5–10 mm (0.2–0.4 in.)) near base. Inflorescence whorled, a compound raceme.
- Leaves: Spirally. Lower leaves quite long-stalked, glabrous. Leaf blade widely ovate, cordate-based, round-tipped, 10–25 cm (4–10 in.) long, twice as long as broad, almost waveless, edges gently curved, underside papillose (surface with small pimples). Stem leaves alternate, narrowly ovate–lanceolate.
- Fruit: Achene 2.5–3.5 mm (0.1–0.14 in.), light brown. Perianth segment lobes narrowly ovate–ovate, blunt-tipped, 4–6 mm (0.16–0.24 in.) long, often toothed (see subspecies), at least one, often all with long tubercle. Flower-stalk (2–10 mm (0.08–0.4 in.)) about twice as long as calyx, joint near base.
- Habitat: Yards, waste ground, roadsides, rich shores.
- Flowering time: August–October.
Genus Rumex is comprised of some 200 species wordwide, of which approx. 20 grow in Finland. They are quite a troublesome group because members easily cross-breed – broad-leaved dock especially with Scottish dock (R. aquaticus), water dock (R. hydrolapathum), curled dock (R. crispus) and northern dock (R. longifolius). The calyx of the ripe fruit is helpful (and often necessary) to identify the plant.
Broad-leaved dock can be differentiated from other genus Rumex plants by its broad, blunt leaves. The leaves of Asiatic dock (R. confertus) are just as wide, if not wider. They can be differentiated by the fact that Asiatic dock’s fruit calyx has a cordate base and is very wide.
In Finland there are three subspecies of broad-leaved dock: ssp. obtusifolius, ssp. transiens and ssp. sylvestris. The easiest way to differentiate the subspecies from each other is according to how toothed the calyx lobes are and if they have pimples. Ssp. obtusifolius has the longest and narrowest teeth and only one pimple; ssp. sylvestris has the shortest teeth and no pimples at all. The pimples on ssp. transiens and ssp. sylvestris are on all three calyx lobes.