The Oxford Dictionary tells me that the word spurge was first used in Late Middle English and is a ‘shortening of Old French espurge, from espurgier, from Latin expurgare “cleanse” (because of the purgative properties of the milky latex)’. If you have sensitive skin, you may want to be wary of touching that latex, which both the stem and leaves will exude if broken, as it can irritate.
In fact, the latex in Petty spurge (Euphorbia peplus) is so caustic that it’s used in medications for the removal of warts and veruccas. This is the spurge I see most often, as it seems to enjoy the edges of pavements and lanes, road verges and waste ground and, though an annual, it can be seen over a long period, from April right through to October.
Sun spurge (Euphorbia helioscopia) is superficially similar to Petty spurge but is slightly larger and has a shorter growing period, from May to August. The easiest way to tell one spurge from the other is by counting the rays in the umbel: Petty spurge has three rays while Sun spurge has five. Although Sun spurge supposedly enjoys a similar growing environment to Petty spurge, I don’t see it very often in my urban area: as the photo below indicates, my find was growing in an arable field (where no crops were sown this season, but some residue crops have sprouted).
Perhaps because of its irritant sap, Sun spurge has a wealth of interesting common names. These are from the Royal Horticultural Society’s website: cat’s milk, churn staff, little good, little goody, mad woman’s milk, mare’s milk, mouse milk, wart grass and wartwort.
Cypress spurge (Euphorbia cyparissias) is the most unusual and intriguing of today’s spurges. I found a large area of this very attractive plant growing on top of the Aberbargoed coal spoil tip on 29 July but it’s taken a couple of weeks to get the identification confirmed. I’m not sure how the plant came to be on the tip – my guide book says Cypress spurge is ‘possibly native’ in southern Britain but a probable garden escape elsewhere (The Wild Flower Key).