Dog's mercury
Mercurialis perennis · Euphorbiaceae
The gardener's calendar
Ideal time to plant dog's mercury: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Foliage
- Deciduous
- Blooming
- February to April
- Adult size
- 20 to 40 cm tall
- Growth
- Moderate
- Hardiness
- Hardy, down to -15°C
- Origin
- Western and central Europe
- Soil type
- Rich, humus-filled, well-drained
Care
Light
Perennial mercury prefers partial shade to full shade, typical of woodland understory. It tolerates indirect morning light but dreads direct sun, which dries out its foliage. In a forest or beneath deciduous trees, it finds its ideal conditions.
Watering
Keep the soil consistently moist without waterlogging, especially during spring growth. In summer and autumn, reduce watering if the soil stays naturally cool. In winter, moderate moisture is sufficient since the plant is dormant.
Soil
Choose soil rich in organic matter and well-structured, similar to forest conditions. Add compost or decomposed leaves in spring to enrich the substrate and promote rooting. Drainage must be adequate to prevent rot.
Pruning
No pruning is necessary; let the plant develop naturally. Simply remove dead or damaged stems and leaves in early spring. This ground cover spreads on its own and requires no regular intervention.
Fertilizer
A very diluted balanced fertilizer in spring is plenty if your soil is rich. Perennial mercury isn't demanding and prefers gradual feeding through organic matter. Avoid excess nitrogen, which promotes weak foliage.
Diseases and pests
This plant is generally hardy and rarely troubled by pests in natural conditions. Powdery mildew may appear in overly dry, warm settings; improve ventilation and humidity. Poor drainage promotes root rot: check water drainage.
Did you know?
In the Middle Ages, perennial mercury was considered a magical plant, associated with the god Mercury because of its Latin name. Once, it appeared in medicinal gardens as a healing herb, though internal use is not recommended. Its old name 'St. Paul's herb' testifies to how deeply rooted it was in European herbal culture.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
Add this plant to my garden →Plants from the same family
- Wood spurgeEuphorbia amygdaloides
- Caper spurgeEuphorbia lathyris
- Albanian spurgeEuphorbia characias
- Spiny spurgeEuphorbia spinosa
- Garden crotonCodiaeum variegatum
- Griffith's spurgeEuphorbia griffithii
Tips generated and checked by Viridia — adapt them to your local climate.