Mercurialis perennis, commonly known as dog's mercury, is a poisonous woodland plant found in much of Europe as well as in Algeria, Iran, Turkey, and the Caucasus, but almost absent from Ireland, Orkney and Shetland. A member of the spurge family (Euphorbiaceae), it is a herbaceous, downy perennial with erect stems bearing simple, serrate leaves. The dioecious inflorescences are green, bearing inconspicuous flowers from February to April. It characteristically forms dense, extensive carpets on the floor of woodlands and beneath hedgerows.
Growth and location
Mercurialis perennis is a herbaceous plant. It usually grows in dense masses often in the ground flora of beech, oak, ash, elm and other types of woodlands in Europe. It also grows under the shade of hedgerows and scrub. It has a preference for moderately shady to densely shady habitats. It is able to colonise new deciduous woods on dry, calcareous soils at an annual rate of a metre or more. but in the open, it eventually gives way to other plants.
Mercurialis perennis extends from sea level to the mountain range. The ultimate height attained in different mountainous regions, e.g. in Scotland, England, Germany, and Switzerland, naturally varies with the latitude and other geographical factors.
The scent of the plant is often described as 'foetid' due to the presence of trimethylamine which often gives off a rotting fish smell. Mercurialine is thought to be one of the active principal parts that are responsible for the toxicity of the herb. Larger doses cause lethargy, jaundice, painful urination, apparently by making the urine acid, and coma before death.
Reported cases of poisonings
The first-known account of this phenomenon probably dates from 1693, when a family of five became seriously ill as a result of eating the plant (after boiling and frying it); one of the children died some days later as a result.
Uses
The dog's mercury is poisonous by itself but with a thorough drying/heating, one is able to destroy its poisonous quality. The juice of the plant is emetic, ophthalmic and purgative. It can be used externally to treat menstrual pain, ear, and eye problems, warts, and sores. A lotion can be made from the plant for antiseptic external dressing due to its ability to soften and moisturise the skin.
A fine blue dye can be obtained from the leaves although it is able to be turned red by acids and destroyed by alkalis. It is often permanent and colouration is similar to indigo. A yellow dye can be obtained from the leaves. The seeds are also a good source of drying oil.