Persicaria maculosa

lady's thumb

SunFull Sun – Part Shade

Overview

Persicaria maculosa (syn. Polygonum persicaria) is an erect to ascending annual in the family Polygonaceae reaching 12-36 inches (30-90 cm) tall and 8-18 inches (20-45 cm) wide. Stems are erect, branching, carrying swollen nodes and papery tubular sheaths (ocreae) at each node. The ocreae have bristle-like cilia (fringes) 1-3 mm long on the upper margin, and this character separates the species from P. lapathifolia. Leaves are alternate lance-shaped 2-6 inches (5-15 cm) long with entire margins. Most leaves carry a dark purplish-brown chevron or thumbprint-shaped blotch in the center of the upper surface, which is the source of the common name 'lady's thumb'. The blotch is variable and occasionally absent. Flowers are pink to purplish-pink, small, in dense ovoid to short-cylindrical erect spike-like racemes 0.4-1.2 inches (10-30 mm) long at stem tips and in upper leaf axils. Each flower carries 4-5 tepals. Fruit is a shiny dark brown to black lens-shaped or trigonous achene. A single plant produces 500-3,000 seeds, viable in soil for 5-10 years. The species occurs widely in moist gardens, cultivated fields, and disturbed ground throughout the Pacific Northwest.

Native Range

Persicaria maculosa is native to Europe and Asia, in cultivated fields, gardens, roadsides, and moist disturbed ground from sea level to approximately 7,000 feet (2,100 m). Naturalized across all 50 U.S. states and all Canadian provinces. The species occurs widely in annual-weed surveys of Pacific Northwest gardens.

Suggested Uses

Used in Polygonaceae identification courses for the ocrea ciliation key: P. maculosa (ciliate, not peppery) versus P. lapathifolia (eciliate) versus P. hydropiper (ciliate, peppery taste). The leaf thumbprint blotch is a secondary diagnostic teaching feature. Seeds are studied in waterfowl diet ecology. Included in annual-garden-weed identification exercises.

How to Identify

Separated from Persicaria lapathifolia (dock-leaved smartweed) by the ciliate (bristle-fringed) ocreae versus the smooth-margined ocreae of P. lapathifolia, and by the pink to purplish-pink flowers versus the greenish-white to pale pink flowers of P. lapathifolia. Separated from P. hydropiper (water pepper) by the absence of a peppery taste when a leaf is crushed and chewed. The dark thumbprint blotch on the leaf center is characteristic but variable. Ocrea ciliation is the single strongest field diagnostic: examine the upper margin of the papery sheath at a stem node for bristle-like fringes 1-3 mm long.

Appearance

Size & Dimensions

Height1' - 3'

Width/Spread8" - 1'6"

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~10 weeks

Summer Fall

Dense pink to purplish-pink spike-like racemes 0.4-1.2 inches (10-30 mm) long at stem tips and upper leaf axils, borne June through October over 8-10 weeks. Self-pollinating and insect-pollinated. Seeds mature 3-4 weeks after flowering. In the Pacific Northwest peak flowering falls in August through September. Seeds are consumed by songbirds and waterfowl.

Detailed Descriptions

Flower Description

Pink to purplish-pink; small flowers in dense ovoid to short-cylindrical erect spike-like racemes 0.4-1.2 inches (10-30 mm); June-October

Foliage Description

Medium green; lance-shaped alternate leaves typically carrying a dark purplish-brown chevron or thumbprint blotch in the center; ocreae with bristle-like cilia on the upper margin; deciduous

Growing Conditions

Sun Requirements

SunFull Sun SunPartial 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 - 8.0(Neutral)

357912

Soil Types

loam silt clay sand

Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Care & Maintenance

Care Guide

Hand-pulling before seed set works because the annual root system is shallow and fibrous and extracts easily from moist soil. Hoeing at the soil surface severs the root crown and is efficient for large populations. In garden beds, mulching with 2-3 inches (5-8 cm) of organic material suppresses germination. The annual habit means plants do not persist from roots. Consistent removal before seed set for 5-10 years depletes the soil seed bank. In agricultural settings, cultivation before seed maturity reduces populations in subsequent seasons.

Pruning

Pruning does not apply in a weed-management context. Plants are pulled or hoed before seed maturity. The annual habit means complete removal prevents regrowth. In dense garden infestations, shallow hoeing in early summer before flowering is the most efficient approach.

✓ Toxicity

Non-toxic

Weeds