Dog's Mercury (Mercurialis perennis)

Dog's Mercury

Mercurialis perennis

Its glossy evergreen leaves carpet shaded woodlands, a quiet understory staple. Perennial herbaceous groundcover; common name: Dog's Mercury.

Low light
1–2/week
Moderate
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Plant Needs

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Sunlight Thrives in deep to partial shade; avoid direct sunlight, which can scorch its delicate foliage
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Watering Keep soil consistently moist but not waterlogged; mature plants can tolerate short periods of dry soil
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Temperature Hardy to -15°C; prefers cool temperate conditions and will wilt if exposed to prolonged temperatures above 25°C
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Characteristics

  • Leaf: Glossy oval to lanceolate leaves with serrated margins, arranged oppositely on stems
  • Flower: Inconspicuous greenish dioecious flowers; male flowers in loose clusters, female flowers in small axillary spikes
  • Stem: Erect, unbranched green stems covered in fine, soft hairs
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Care Guide

Watering

Keep soil evenly moist; apply mulch to retain moisture and suppress weeds

Fertilization

Apply diluted compost tea once monthly to support new growth. Avoid high-nitrogen fertilizers, which can encourage leggy growth

Composted banana peel tea:Fully compost banana peels before use; dilute 1:20 with water for root drenching to avoid attracting pests or causing soil imbalances
Pruning
  • Remove yellowing or damaged foliage in early spring to improve airflow and maintain a tidy appearance
  • Thin dense clumps every 2–3 years to prevent overcrowding and reduce disease risk
  • Cut back spent flower stems after blooming to redirect energy to foliage growth
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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 mercurialin alkaloids; ingestion causes gastrointestinal distress, dizziness, and headache

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Garden Uses & Culture

Culture: N/A

Usage: Limited ornamental use as a woodland groundcover; avoid planting in areas accessible to pets or children due to toxicity