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. However, the total length of spurge root per unit of soil is about a third less than that of native grasses, so its presence increases soil erodability. Seed disperses up to 5 m following an explosive capsule rupture and the seeds float, so the flood plains of many prairie rivers are infested, but it is also spread in gravel, animal feed and sheep, grazed on spurge, distribute viable seed in their droppings.
Many prairie farmers claim their infestations originated with hay imported in the dirty thirties.
Spurge is killed by a combination of cultivation and 2, 4-D, but the roots often survive either treatment alone 2 . Eradication with picloram requires maintaining soil residues of 50 ppb for 8-10 years, which is not economic or ecologically desirable for large infestations. The latex is a co-carcinogen and produces dermatitis in humans and livestock. Sheep graze spurge, particularly the young shoots, but the clones vary in palatability and spurge returns to its former density in two years of sheep removal. Tetraploid cypress spurge is a similar problem in eastern Canada where it is particularly dense on limestone and sandy soils.