The pistil is a distinct part of the female plantâ€™s reproductive organ and is identified on cannabis as the small hair-like extensions on the buds that vary in color. Pistils are often confused with stigmas, although the pistol is the part that the stigmas grow out of. The pistil collects pollen from the male plants when being fertilized. The appearance of the pistils changes color over time. When cannabis plants are left unfertilized, the pistils will begin to change colors and can be an indicator of ripeness.
Photoperiod strains will often start to produce pistils shortly after the light cycle is reduced for indoor growing or seasonal light decreases when growing outdoors. Autoflowering varieties would typically begin to develop pistils around three to four weeks.