Overview
Rumex obtusifolius is a taprooted perennial in the buckwheat family (Polygonaceae) reaching 24–48 inches (60–120 cm) tall with a 12–24 inch (30–60 cm) spread, arising from a stout, fleshy, yellow taproot similar to R. crispus. Stems are erect, stiff, grooved, branching in the upper half. Basal leaves are broadly ovate, 6–14 inches (15–35 cm) long and 3–8 inches (8–20 cm) wide, with a cordate (heart-shaped) base and an obtuse (blunt-rounded) tip — much broader and wider than the lance-shaped leaves of R. crispus. Leaf margins are flat to slightly wavy (not strongly crisped). Stem leaves are smaller, alternate, with papery ocreae at the nodes. Flowers are tiny, greenish, in dense whorls on branching panicles. Fruit is a triangular achene enclosed in 3 enlarged valves, each 0.16–0.24 inch (4–6 mm) long, with prominent teeth (spiny projections) on the margins and usually a single prominent grain — the toothed valve margin is the primary distinction from R. crispus. A single plant produces 20,000–60,000 seeds, viable in soil for 50–80 years. Contains oxalic acid; toxic to livestock in quantity. Hybridizes readily with R. crispus to produce R. x pratensis, which shows intermediate leaf and fruit characters.
Native Range
Native to Europe and western Asia, occurring in pastures, gardens, roadsides, and moist disturbed ground from sea level to approximately 7,000 feet (2,100 m). Naturalized across most of the United States and all Canadian provinces. Common in the Pacific Northwest, often co-occurring with R. crispus in the same habitats.Suggested Uses
Used in Polygonaceae identification courses for the fruit valve comparison: toothed margins (R. obtusifolius) versus entire margins (R. crispus) versus absent valves (R. acetosella). The three-species Rumex comparison (small arrow-leaved R. acetosella, lance-leaved curly R. crispus, broad-leaved flat R. obtusifolius) is a standard teaching unit in weed identification. The hybridization with R. crispus is studied in invasion genetics. In European folk medicine, dock leaves are traditionally applied to nettle stings.How to Identify
Appearance
Size & Dimensions
Height2' - 4'
Width/Spread1' - 2'
Bloom Information
Flowers from June through August, slightly later than R. crispus. Dense, whorled panicles bloom from the base upward over 3–4 weeks. Wind-pollinated. Seeds mature by August in the Pacific Northwest. Reddish-brown seed stalks persist through fall and winter.Detailed Descriptions
Flower Description
Greenish, becoming reddish-brown at maturityFoliage Description
Dark green, broadly ovate with a cordate (heart-shaped) base and obtuse tip; margins flat to slightly wavy; underside often with prominent veinsGrowing Conditions
Sun Requirements
Requires 4-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight