Woolly Mercury (Mercurialis tomentosa)

Woolly Mercury

Mercurialis tomentosa

Soft woolly foliage adds muted texture to wild edges. Perennial herbaceous groundcover; common name: Woolly Mercury.

Partial sun
0–1/week
Beginner
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Plant Needs

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Sunlight Partial shade to full sun; tolerates dry, rocky conditions; avoid intense midday sun in hot climates
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Watering Drought-tolerant; water only during prolonged dry spells; avoid overwatering to prevent root rot
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Temperature Hardy to mild frosts; prefers cool to temperate temperatures; avoid extreme heat above 32°C
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Characteristics

  • Leaf: Oval to lanceolate leaves covered in dense white woolly hairs, opposite arrangement
  • Flower: Inconspicuous greenish dioecious flowers, borne in axillary clusters
  • Stem: Erect to trailing stems with soft tomentose covering
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Care Guide

Watering

Water sparingly only when soil is completely dry

Fertilization

Optional diluted compost tea once per growing season. No regular fertilization needed; excess nutrients may reduce drought tolerance

Composted eggshell powder:Sprinkle a thin layer on soil surface in early spring to support root health; avoid direct contact with foliage to prevent irritation
Pruning
  • Trim back spent flower stems to maintain tidy growth and prevent self-seeding
  • Remove yellowing or damaged foliage to improve airflow
  • Thin overcrowded clumps in early spring to reduce disease risk
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Toxicity

Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA: Toxic; ingestion may cause vomiting, diarrhea, abdominal pain, and lethargy

Humans: Contains toxic alkaloids; ingestion causes gastrointestinal irritation, nausea, and vomiting

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Garden Uses & Culture

Culture: N/A

Usage: Groundcover for rock gardens, wildflower meadows; erosion control on sunny slopes