Euphorbia lagascae and Centrapalus pauciflorus are natural sources of the plasticizer vernolic acid, and are therefore being considered as potentially new industrial oilseed crops in Canada. Both species show a propensity to grow in undisturbed and unfavourable conditions in their native regions of southern Europe and Africa. Trials were conducted in Ontario between 2013 and 2014 to better understand the biology of these species. The ability of these species to establish, leave a seedbank, and compete with a crop was explored. C. pauciflorus emergence in cultivated seedbeds (5.14%-12.15%) was higher than in mowed (0.99%-1.87%) and undisturbed grass (0.00%-0.25%) in spring 2014. E. lagascae also emerged at higher rates in cultivated seedbeds (3.07%-4.98%) than mowed (0.88%-1.99%) or undisturbed grass (0.22%-1.00%) in spring 2014, however emergence was higher in mowed grass (6.25%) than seedbeds (4.00%) in fall 2014. The low persistence of seeds in the soil (93%-100% seeds were nonviable) and poor ability to establish a seedbank limit their potential as weeds. Plants that established in unmanaged areas did not produce viable seeds and are therefore unlikely to become weeds. Even though their competitive ability is similar to that of redroot pigweed on a plant per plant basis, they are unlikely to achieve the high densities and persistence of pigweed infestation and are unlikely to threaten farms as weeds.