The vegetative stage is when your cannabis plants are growing and developing. The length of time you spend in this stage will depend on a few factors, including the size of your grow operation and the strain you're growing. In general, though, most growers will keep their plants in the vegetative stage for 4-8 weeks before switching to the flowering stage. The main reason for this is that it takes time for your plants to reach their full potential size. If you switch to the flowering stage too early, your plants will be smaller and produce less bud. However, if you wait too long to switch, your plants may become stressed and produce less bud as well. As a general rule of thumb, indica strains tend to mature faster than sativa strains. This means that you can usually get away with a shorter vegetative stage for indica strains (4-6 weeks) than sativa strains (6-8 weeks).