Common Names: Dog’s mercury,boggard posy.
Habitat:Dog’s mercury is native to Europe, including Britain, from Scandanavia south and east to Spain and S.W. Asia.It is abundant at Hythe in Sussex.But is almost absent from Ireland, Orkney and Shetland.It grows in Woods and shady places, usually in beech and oak woods, avoiding acid soils.
Dog’s Mercury, a perennial, herbaceous plant, sending up from its creeping root numerous, undivided stems, about a foot high.Each stem bears several pairs of rather large roughish 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.
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It is hardy to zone 4 and is not frost tender. The flowers are dioecious (individual flowers are either male or female, but only one sex is to be found on any one plant so both male and female plants must be grown if seed is required) and are pollinated by Wind, flies.
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. 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.The plant is not self-fertile.
Dog’s Mercury has a disagreeable odour and is extremely acrid, being poisonous to animals in the fresh state. It has been said, however, that heat destroys its harmfulness, and that it is innocuous in hay. Its chemical constituents have not been ascertained.
Dog’s Mercury has proved fatal to sheep, and Annual Mercury to human beings who had made soup from it.
Dog’s mercury is poisonous in the fresh state, though thorough drying or heating is said to destroy the poisonous principle. The fresh juice of the whole plant is emetic, ophthalmic and purgative. It is used externally to treat women’s complaints, ear and eye problems, warts and sores. A lotion made from the plant is used for antiseptic external dressings. A homeopathic remedy is made from the plant. It is used in the treatment of rheumatism, dropsy, diarrhoea and disorders of the gall bladder and liver.
A fine blue dye is obtained from the leaves, it is turned red by acids and destroyed by alkalis but is otherwise permanent. It resembles indigo. A yellow dye is obtained from the leaves. The seed is a potential source of a very good drying oil.
The leaves contain trimethylamine and, in the early stages of putrefaction or when bruised they give off the smell of rotting fish
Known Hazards: All parts of the plant are highly poisonous.As Methylamine (mercurialine) and trimethylamine are thought to be present, together with a volatile oil and saponins. Symptoms of poisoning appear within a few hours; they can include vomiting, pain, gastric and kidney inflammation, and sometimes inflammation of the cheeks and jaw (“malar erythema”) and drowsiness. 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.
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