Dog’s Mercury

Found mainly in woodlands and hedgerows, Dog’s Mercury is far from showy, but is distinguished by being one of the earlier plants to flower each year.
Photo: Steve Townsend


Scientific name: Mercurialis perennis

Other common names: Dog’s Cole, Adder’s Meat, Lasting Mercury

Dog’s Mercury has been described as ‘not a spectacular plant, except in sheer weight of numbers and power to keep all rivals from its chosen ground’ (Gilmour and Walters, 1954). Mainly found in woodlands, hedgerows and shadier places, this hairy-stemmed perennial does indeed often grow locally in some abundance, spreading from creeping rhizomes below the ground. While it is a native (it is an indicator species for ancient woodland in some parts of the country), it can sometimes be a problem when it colonises newer woodland, preventing other plants with higher light requirements from becoming established.

It may not be spectacular, but Dog’s Mercury is one of the harbingers of returning Spring, flowering from February to April. It is a dioecious plant (i.e. male and female flowers are on separate plants). On male plants, spikes of greenish flowers with yellow stamens appear in the axils of the paired, hairy elliptical leaves, while the female plants produce small clusters of flowers on stalks. It is mainly wind-pollinated. The flowers are not at all sweet-smelling, and the plant is very poisonous if consumed, causing vomiting, diarrhoea and, in more severe cases, jaundice and coma. It is toxic even to most invertebrates, with a few exceptions, such as the Dog’s Mercury Flea Beetle (Hermeophaga mercurialis) and caterpillars of the Square-spotted Clay Moth (Xestia rhomboidea ).

Dog’s Mercury prefers basic or calcareous soils, and is therefore at home on the serpentine of The Lizard.

Did you know…?

…a ‘dog’s plant’ is one that was considered to have no medicinal properties.

…with its preference for alkaline soils, Dog’s Mercury can also be found away from woodlands on limestone pavements.

More information and references:

Gilmour, J. and Walters, M., 1954. Wild Flowers: Botanising in Britain (New Naturalist Series). Collins, London.

Mabey, R., 1997. Flora Britannica. Chatto & Windus, London.

Proctor, M., 2013. Vegetation of Britain and Ireland (New Naturalist Series). Collins, England.

Rose, F. and O’Reilly, C., 2006. The Wild Flower Key, 2nd edition. Frederick Warne, London.

Published: March 2014
Author: Amanda Scott
Photos: Steve Townsend