The entire cannabis plant, aside from the inside of the stems and the roots, does contain certain cannabinoids. Some parts only produce/contain trace amounts of CBD and THC, so it is probably not worth your while to worry about these parts at harvest time. The parts for the plant you do want to focus on are the buds and small leaves surrounding the buds, which grow  on the female plant and will be sparkling with trichomes. The buds and small leaves which surround the buds have a fine layer of hairs and white crystals on the surface. The crystals are the trichomes and contain the greatest concentration of THC and the cannabinoids like CBD. So you need to wait for the plants to flower and produce buds and you should be able to see these sparkling crystals on the maturing buds.  These are the best part to vaporize or smoke. If you want to learn more about the best vaporizer, check out our information pages:  Here Check out vaporizers at our shop guide site: Here