Broad-leaved dock (Rumex obtusifolius, L. 1753)

Identity

Broad-leaved dock (Rumex obtusifolius L., 1753), also called Bitter dock or Butter dock, is an herbaceous perennial in the genus Rumex, family Polygonaceae. Plants of the World Online accepts this name for a species native to Europe, temperate Asia as far as central Siberia and Iran, and northwestern Africa. ^{1 6}

Rounded rather than pointed leaf tips explain the epithet obtusifolius. Compared with the narrower foliage of several other Rumex species, its wide leaves also give Broad-leaved dock its English name. ⁷

Recognition

Large oval to oblong basal leaves form the first rosette of Rumex obtusifolius. They have heart-shaped bases and commonly measure 25–30 cm (10–12 in) long by 12–15 cm (5–6 in) wide. The edges are slightly wavy rather than strongly curled. ^{2 8}

Branched flowering stems stand 40 cm–1.5 m (16–59 in) tall, with increasingly narrow leaves toward the top. Small bisexual, wind-pollinated flowers form dense whorls along the stem, turning from greenish to reddish as they mature. ²

Fruits provide a firmer identification than leaf shape, particularly in a young rosette. Each achene is enclosed by three persistent valves, 3.5–6 mm (0.14–0.24 in) long, each with 2–5 marginal teeth. Only one valve has a conspicuous central swelling, or tubercle. ⁸

Useful taxonomy

Under the accepted name Rumex obtusifolius L., published in 1753, Kew places this dock in Polygonaceae, subfamily Polygonoideae. ^{1 7}

Geographic range is the main distinction among several recognized subspecies:

• Rumex obtusifolius subsp. obtusifolius predominates in western Europe and is the type subspecies;
• Rumex obtusifolius subsp. transiens (Simonk.) Rech.f. ranges from central Europe to the western Caucasus.

Regional French floras use several vernacular names referring to its blunt leaves or wild occurrence. These names all refer to Broad-leaved dock, rather than to distinct species. ⁶

Habitat and range

Europe, temperate Asia as far as central Siberia and Iran, and northwestern Africa constitute the native range POWO records for Rumex obtusifolius. Introductions have since brought it to almost every temperate continent. ^{1 9}

Nitrogen-rich, repeatedly disturbed ground strongly favors establishment, whether on waste land, roadsides, riverbanks, ditches, pasture or cultivated fields. Abundant plants can indicate compacted soil overloaded with organic matter. In contrast, establishment slows markedly on poor, dry ground with little available nitrogen. ^{4 8}

A sturdy, branched taproot reaches down to 2 m (6.6 ft). It draws on available water and nutrients even in poor soil, helping explain how the plant can persist there once established. ⁸

Life cycle and reproduction

Bisexual, wind-pollinated flowers appear during June–October in the temperate Northern Hemisphere calendar described here, depending on climate. A single Rumex obtusifolius flowering stem produces both pollen and seeds, unlike Rumex acetosa, whose male and female flowers occur on separate plants. ²

About 60,000 seeds can develop on one flowering stem and remain viable in soil for several years. This output explains why an infested field may stay affected for several seasons after an initial attempt at removal. ⁸

Besides seed reproduction, a root fragment left in soil can regenerate a whole plant. Pieces within 12 cm (5 in) of the surface regrow readily, so mechanical removal remains incomplete unless repeated. ³

Uses and risks

Food use is marginal, restricted to very young leaves sometimes described as edible after cooking. Bitterness develops early in the season, clearly distinguishing this dock from the more valued culinary sorrel, Rumex acetosa. ⁴

Traditional herbalism used the tannin-rich root as an astringent and in infusions for jaundice or skin eruptions. Fresh leaves were applied externally to burns and blisters. Strong clinical evidence does not currently validate any of these uses. ⁴

Soluble oxalates occur in the foliage. According to ASPCA, substantial ingestion of plants in the genus Rumex, which includes Rumex obtusifolius, can cause tremors and excessive salivation in dogs, cats and horses, with kidney damage a rarer risk. ⁵

Rubbing the underside of a leaf on a nettle sting is a widespread folk practice in the UK and Ireland. No scientific evidence confirms an effect beyond cooling contact on the skin or simple distraction. ⁴

Varieties, look-alikes and related plants

Horticultural selection is not documented for Rumex obtusifolius: it remains a wild weed, rather than an ornamental or vegetable crop. Only botanical subspecies, distinguished by geographic range, are recognized. ⁷

Two related docks and sorrels warrant comparison:

• Rumex crispus, Curled dock, has much narrower, strongly wavy leaves and fruit valves with smooth rather than toothed edges;
• Rumex acetosa, Common sorrel, is smaller, dioecious and much more acidic in taste, cultivated as a vegetable rather than treated as a weed.

Before bolting, young rosettes of Rumex crispus and Rumex obtusifolius can look very similar because fruits are not yet available for comparison. Once fruits develop, 2–5 teeth on the valve edges identify Rumex obtusifolius; their absence points toward Rumex crispus. ⁸

Main sources

• Plants of the World Online / Kew, Rumex obtusifolius L.
• Royal Horticultural Society, Rumex obtusifolius - broad-leaved dock
• Royal Horticultural Society, Docks - weeds advice
• Plants For A Future, Rumex obtusifolius
• ASPCA, Dock (Rumex sp.) toxicity entry
• Integrated Taxonomic Information System, Rumex obtusifolius L.
• USDA GRIN Global Taxonomy, Rumex obtusifolius L.
• Weeds Australia, Broad-leaved Dock (Rumex obtusifolius) profile
• VicFlora / Royal Botanic Gardens Victoria, Rumex obtusifolius