The vegetative growth stage for Cannabis plants usually takes place between week #2 & week #5, depending on how big your marijuana plants are and what strain you are growing, as every strain has its own specific life cycle. The Vegetative Cannabis Growth Stage is the growing stage between seedling growth/cloning and the flowering stage.IMPORTANCE OF THE VEGETATIVE PHASE. The vegetative phase is a vital period in the life cycle of a cannabis plant. Growers need to provide optimal environmental conditions for their plants to grow as large and healthy as possible. Vegetative Stage Of A Plant ,See the best tips for vegetation stage of marijuana. For todays piece about vegging cannabis we will assume that you have planted your seeds or cuttings already. After the process of propagation small and fresh baby plants have started to grow.