Dog's mercury

Dog's Mercury

©Philip Precey

Dog's mercury

Scientific name: Mercurialis perennis
Often seen carpeting the floor of ancient woodlands, Dog's mercury can quickly colonise, its fresh green leaves shading out rarer plants. It is also very poisonous.

Species information


Height: up to 35cm

Conservation status


When to see

January to December


A common plant, often seen carpeting the floor of ancient woodlands, Dog's mercury can quickly colonise and spread by its underground rhizomes (stems). It can be so expansive that it shades woodland floors and crowds out rarer species like Fly orchid and Oxlip. It produces small flowers from February to April, but leaves can persist throughout the year.

How to identify

Dog's mercury has spear-shaped, toothed, fresh green leaves carried on upright stems. It produces a foul and rotten smell, and bears clusters of small, greenish flowers in spring.



Did you know?

Unlike the 'true' mercuries (Chenopodiumspecies such as Good-King-Henry), Dog's mercury is highly poisonous and hence became known as 'False mercury' or 'Dog's mercury'. Ingestion of this plant can lead to vomiting, jaundice, coma and eventually death.

How people can help

The Wildlife Trusts manage many woodland nature reserves sympathetically for the benefit of all kinds of wildlife. A mix of coppicing, scrub-cutting, ride maintenance and non-intervention all help woodland wildlife to thrive. You can help too: volunteer for your local Wildlife Trust and you could be involved in everything from traditional forest crafts to surveying for woodland plants.