What hardiness zones is Rumex obtusifolius suitable for?

Rumex obtusifolius is suitable for USDA hardiness zones 3, 4, 5, 6, 7, 8, 9.

What are the sun requirements for Rumex obtusifolius?

Rumex obtusifolius requires Full Sun.

How much water does Rumex obtusifolius need?

Rumex obtusifolius has Medium water needs.

Herbaceous

Rumex obtusifolius

broad-leaved dock

PolygonaceaeEurope, western Asia

At a Glance

TypePerennial

HabitUpright

FoliageDeciduous

Height24-48 inches (60-120 cm)

Width12-24 inches (30-60 cm)

Growing Zones

USDA Hardiness Zones

3 - 9

Zone 3

Zone 4

Zone 5

Zone 6

Zone 7

Zone 8

Zone 9

These zones indicate the coldest temperatures this plant can typically survive.

Frost Tolerancehardy

Key Features

Drought Tolerant

Maintenancehigh

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

Distinguished from Rumex crispus (curly dock) by the broadly ovate leaves with a cordate base and flat margins (versus lance-shaped leaves with strongly curly-wavy margins), and the fruit valves with toothed (spiny) margins (versus entire, smooth margins). Both species are similar in overall size and habit and often co-occur. The fruit valve is the definitive diagnostic: examine the mature seed valves for teeth along the margin (R. obtusifolius) versus smooth margins (R. crispus). Hybrids (R. x pratensis) show intermediate characters.

Appearance

Size & Dimensions

Height2' - 4'

Width/Spread1' - 2'

Colors

Flower Colors

green

red

Foliage Colors

green

Fall Foliage Colors

red

Bloom Information

Bloom Period

~4 weeks

Summer

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 maturity

Foliage Description

Dark green, broadly ovate with a cordate (heart-shaped) base and obtuse tip; margins flat to slightly wavy; underside often with prominent veins

Growing Conditions

Sun Requirements

Full Sun

Partial Shade

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

Soil Requirements

pH Range5.0 - 7.5(Neutral)

357912

Soil Types

loamclaysilt

Drainage

moist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

1-2 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Management is identical to R. crispus: digging the fleshy yellow taproot to a depth of 8–12 inches (20–30 cm) is the most effective approach. The stout taproot resprouts from fragments left in the soil. Repeated cutting every 2–3 weeks during the growing season over 2–3 years depletes root reserves. The long-lived seed bank (50–80 years) means eradication requires sustained management over decades. In pastures, the bitter, oxalate-rich leaves are avoided by livestock, allowing the species to increase in grazed areas. Hybridization with R. crispus complicates identification and management in mixed populations.

Pruning

No pruning applicable. Plants are dug, extracting 8–12 inches (20–30 cm) of the fleshy yellow taproot. Cutting flower stalks before seed maturity prevents seed dispersal. Seed heads must be bagged if cutting occurs after seeds have begun to mature.

Maintenance Level

high

⚠️ Toxicity Warning

Toxic to pets