Annual Mercury on bare ground, Portland,Dortset
Spikes of male flowers
Close-up of male flower spikes
Close-up of male flower
Branched, angular stem
July to October
It is found predominantly in the Southeast, the South and the
near Southwest. It is thinly scattered elsewhere.
For a map see the National Biodiversity Network Gateway
It is an archeophyte, which was introduced from Roman times
and probably since.
It grows on nutrient-rich, disturbed, open, bare areas such as
cultivated ground, tips, quarries and roadsides.
It may be increasing.
Annual Mercury is an annual herb growing up to 50cm.
Male and female flowers are usually on different plants.
The male flowers are arranged in clusters on erect spikes.
Individual flowers are up to 5mm and have 3 perianth
segments and up to 15 stamens.
Female flowers are in clusters or solitary in the axils of leaves.
They are similar to male flowers and have 2 styles and up to 3
The fruits are globular, bristly and up to 4mm.
Lower leaves are ovate and upper leaves oval-lanceolate.
They are regularly toothed.
Stems are erect, branched and angular.
When broken they produce a watery, milky fluid.
There are reports of Annual Mercury causing poisoning.
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