Spurge, (genus Euphorbia), one of the largest flowering-plant genera, with 2,420 species, many of which are important to man as ornamentals, sources of drugs, or as weeds. The genus takes its common name from a group of annual herbs used as purgatives, or spurges, mainly the 1-metre- (3.3-foot-) tall European E. lathyris, seeds of which were once used for their laxative effect.