Dogs mercury (mecurialis perennis)

Dog's Mercury is a spring flower found across Europe, but almost absent from Ireland, Orkney and Shetland. This plant favours alkaine (basic) soils and can be found in abundance in limestone regions particularly in Yorkshire.

It is frequently found covering large areas in dense stands as an understorey plant in woodlands, it also favours deep shade and can survive in semi-shade, however in areas of high light intensity Dog's Mercury will give way to different plants.

Dog's Mercury, a perennial, herbaceous plant, sending up from its creeping root numerous, undivided stems, about a foot high.

It is a hairy dioecious perennial with erect stems bearing several pairs of rather large, simple, serrate leaves, and from the axils of the upper ones grow the small green flowers, the barren on long stalks, the fertile sessile, the first appearing before the leaves are quite out. The stamens and pistils are on different plants. The perianth is three-cleft to the base. The barren flowers have nine stamens or more, the fertile flowers two styles and two cells to the two-lobed ovary.

It flowers from the end of March to the middle of May and seeds in the summer. The leaves of the male flowering plants are more pointed and less serrated than those on the female plants, which have longer stalks.

Male and female plants are rarely found intermixed, each usually growing in large patches. The female are less common than the male, and the plant increases more by the spreading of its creeping rootstocks and stems than by seed.

Dog's Mercury has a disagreeable odour and is extremely acrid, being poisonous to animals in the fresh state. Dog's Mercury has proved fatal to sheep, and Annual Mercury to human beings who had made soup from it. It has been said, however, that boiling or drying destroys its harmfulness, and that it is innocuous in hay.

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