Leafy spurge is a perennial rangeland weed from the European steppes that grows in dense patches. Leafy spurge has deep vertical as well as horizontal roots.
Cypress spurge is of Mediterranean-western Europe origin and is more genetically uniform.
Cypress spurge hybridizes with the hexaploid leafy spurge to produce intermediate forms, but most plants are easily distinguished as cypress spurge leaves are narrow and those of leafy spurge are elongate ovals. Leafy spurge dominates herbaceous communities on open to lightly shaded dry sands and gravels as well as moist loams and clays, and tolerates spring flooding. The aggressiveness of spurge seems to be related to symbiotic associations with mycorrhizal fungi that enhance its nutrition in dry, nutrient-poor soils and in competitive situations. Infected six week old spurge seedlings grown with needle and thread grass had significantly more leaves than those without mycorrhiza, which suggests there is nutrient tansfer from the grass to the spurge. Deep vertical roots enable spurge to remain green in dry weather and the horizontal roots produce clones that are several metres in diameter and often visibly different from each other.