Dog’s mercury (Mercurialis perennis) is one of those mysterious, usually nameless, plants that is hardly ever noticed. It forms dense carpets on the woodland floor and beneath old hedgerows but appears to most passers-by as just background for the bluebells and primroses.
It flowers very early in the spring. Its tiny green flowers appear in February and you can see it growing in the ancient hedges at Fiveways.
It spreads rapidly via underground rhizomes. A well established woodland colony can extend its range by a metre every year and can quickly crowd out other woodland floor species.
It is highly poisonous; eating it can lead to vomiting, jaundice, coma and even death so treat it with care. Unfortunately, it looks like several unobtrusive green-flowering species of plants that are edible: Good-King-Henry, markery, English mercury, or mercury goosefoot. The name dog’s mercury means false or inferior mercury which suggests that mistakes were made in the past.
Southwick Country Park Nature Reserve 