Information on Annual Mercury

Common Name: Annual Mercury
Scientific Name: Mercurialis annua
Irish Name: Lus glinne beag
Family Group: Euphorbiaceae
Distribution: View Map (Courtesy of the BSBI)
Flowering Period


Click for list of all flowering by month
Annual Mercury is not easily confused with other wild plants on this web site.


This is an erect, almost hairless annual which grows to about 50cm high, with branching stems.  It is found mainly on waste ground, gardens and cultivated soils. It bears spikes of small 2-4mm, yellowish-green, almost-stalkless flowers, on separate-sex plants, from July to October. It has shiny green, narrow-ovate, toothed leaves. Its fruit is bristly. Annual Mercury is an introduced species which belongs to the Spurge or Euphorbiaceae family, and is now mainly found in the south and east of Ireland. 

I first spotted this wildflower in Sallynoggin, Co Dublin in October 2014 when I also photographed it. 

If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre

Mercury, Annual
Mercury, Annual

According to ‘The Flora of the County Dublin’ (1904) by Nathaniel Colgan, Annual Mercury’s first record was in 1794 when it was ‘Plentifully in waste and cultivated ground’. Colgan writes: ‘This is one of the most characteristic species of County Dublin, where it has its Irish head-quarters, chiefly in and around the city. In the city proper it grows yearly rarer with the increase of buildings, but spreads rapidly outwards, especially towards the coast. Its present limits are Balbriggan on the north, Killiney on the south, and Blanchardstown on the west. Within these limits, however, its distribution is by no means continuous.’