Annual, spreading by seed, it grows on cultivated ground or paths to a height of between 10 and 30 cm depending on the situation. It prefers shade.
The tiny green flowers have no petals, but are surrounded by lime-coloured bracts and occur from April to October.
The hairless stems exude a white latex when cut or crushed. This can be a skin irritant, especially if acted on by sunlight. Also because of this corrosive effect it has been used in folk medicine as a remedy for sun spots, warts, corns and skin cancers. A recent report in the British Journal of Dermatology cited a study into the use of the sap to treat non-melanoma skin cancers. The active ingredient in the sap is called Ingenol Mebutate (aka. Ingenol-3-angelate or Ingenane) and the results have been quite encouraging.
It is not a particularly invasive weed, but a nuisance if it sheds seeds, as it keeps popping up.
It is easily uprooted and the fibrous roots do not regrow. A contact herbicide such as Paraquat should knock it back.
Sun Spurge Euphorbia helioscopia is similar, but usually taller with more elongated leaves. The common name Milkweed is also used for Smooth Sow-thistle (Sonchus Oleraceus) which is no relation.