Jwjohanswered grow question 5 years ago You can grow on a 12/12 "flowering" lighting cycle from seed! Look up "12/12 from seed". A cannabis plant cannot enter flowering until it has matured, which usually takes 3 or 4 weeks after it sprouts. After that, you can flower whenever you want! In fact, auto-flowering strains usually begin flowering automatically around 4 weeks regardless of the light cycle. Just remember that a cannabis plant may stretch out to 2x its current height, so make sure you do it with a plan. Don't end up with a 10 foot tall flowering plant in a house with 8 foot tall ceilings LOL It's also extremely important that during those 12 hours of darkness, the plant remain in darkness. Any interruptions can bring it out of flowering.