The Mercuries
What are they?
This is a small group that in our region contains just two species. The mercuries are in the spurge family but are very different in appearance from the typical spurges. They are broad-leaved species with the male and female flowers being carried on separate plants.
Where are they found?
The two species are rather different in their lifestyles, with Dog's Mercury being a spreading perennial of woodland while Annual Mercury is a weed of disturbed ground, typically in gardens and - especially - allotments, where the soil has been enriched.
Identification
While the two species are superficially rather similar in their flowers and leaves, they can readily be told apart by their growth style and by location.
Dog's Mercury Mercurialis perennis
Native. Common and often abundant and carpeting the ground in shady areas and woodland, although rare on lighter, sandy or chalky soils. A useful indicator of ancient woodland sites and often persistent under roadside hedges long after the woodland has been cleared. Flowers February to April. This species forms extensive spreading colonies of unbranched, upright stems, arising in spring from a creeping rootstock. The opposite leaves are shiny, but less so than Annual Mercury and are clearly stalked.
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Annual Mercury Mercurialis annua
An ancient archeophyte, introduced before Roman times from mainland Europe. Rather patchily-distributed across the region but often common where it occurs, such as around Norwich, Great Yarmouth/Lowestoft, southeast Suffolk and parts of the Fens. Flowers mostly July to October but occasionally at other times. An annual that produces many-branched stems with glossy, more or less stalkless leaves.
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