You plant cannabis seeds… and harvest cannabis plants! In their natural environment (outdoor) plants will begin to bud when the hours of light and darkness change as the season passes from Summer to Autumn, so flowering takes place between September and November in the Northern hemisphere. In an artificial environment (grow room), light management controls the growing (vegetative) and the flowering (budding) stages. Typically 18 hours of light / 6 hours of darkness is used to keep a plant in vegetative state for 2 – 4 weeks, before switching the timer to 12 hours of light /12 hours of dark for flowering. A good cannabis strain description will give details of expected plant growing times and a guide to when to harvest.
The exception to this rule is the autoflowering cannabis plant, which will flower automatically, 60 – 75 days after the seed has been planted. The reason for this ‘auto’ behaviour is the presence of cannabis ruderalis genes in the strain. This short, stubby cannabis plant naturally grows in the Arctic Circle and has adapted its behaviour to live through 24 hour daylight during the summer. By harnessing these genes, cannabis breeders have developed a plant that is shorter in stature and quick to finish without a rigid light/dark hours program.