Contrary to some rumors, a plant cannot be made CBD-rich if it lacks the right genetic make-up. The ratio of THC, CBD, and other cannabinoids is genetically determined, according to a study by biochemist Etienne de Meijer, Inheritance of the Cannabinoid Phenotype. A grower can, however, influence overall cannabinoid content by manipulating environmental factors—temperature, light, water acidity, and nutrients—that affect plant health.