Increasing dark time will push preflowering?

A question from a fellow grower:

Now I have a question… If I keep my plants on a longer dark cycle will pre-flowers be more likely to occur for determining gender? Ive got them on a 17/7 light schedule just for accuracy of summer lighting assuming it gets dark around 9 light around 4. Wondering if increasing dark time will help to push plants into pre-flowering.

Yes longer darkness should force them to start pre- flowering . But I would do it in intervals by weeks . 18/6 two weeks , than 16/8 two weeks , than 14/10 two weeks and than 10/14 to finish . I’ve done it like this a couple times and it really helped resin production .

1 Like

Actually, pre-flowers are pre-flowers and have little to do with light period.

In general regular photoperiod cannabis (as opposed to auto-flowering) will show pre-flowers at a certain size or age, but not all strains will show pre-flowers at all, regardless of light cycle.

In general, you do not need to emulate your local season’s light period/cycle, and for cannabis, generally you need a solid 12 hours of complete darkness to get the plants to flower. Some will flower as the light decreases and maybe start flowering with as little as 10 hours of dark. But indoors 10 hours of dark is almost never used for flowering because there are numerous things that influence the hormonal changes that lead to flowering, the main one is the overall length of the dark period (12 or more hours), but the daily change or lengthening of the dark period (10 hours of dark and increasing daily) combined with temperatures dropping, all of these will combine to influence flowering on a plant outdoors, and this is why you may see flowering outdoors without there actually being a solid 12 hours of darkness yet.

If you need to sex the plant early, playing around with the main plant’s light cycle is not the way to do it. What you do, is take a cutting from an underdeveloped branch lower on the plant, one you would likely prune from the plant later anyway, and you put it in a cloning medium to keep it alive, and you separate it and put it in a 12/12 hour light/dark cycle, and in a couple of weeks or less, it will show its sex, maybe even before showing new roots. Then you know the parent plant is the same sex.

Happy growing,


MacG names says who advice you should take , he is the science officer , I’m just a piñon that happen to read a lot and follow instructions that him and Latewood advised me on , so my information is not in fact valid all the time , I try to re-write what I’ve read either here on the best forum on the inter web to help rookies , newbies , beginners , and somethings I migh can answer , but also scientific things I not so smart to that information . But if any advice you follow , don’t follow mines , it’s best to follow Macgyverstoner because he is my protege , but I’ll never reach his level of wisdom on the whole agriculture knowledge . So my intention is not to confused or create misunderstanding , I be trying to help to much with unknowledgeable facts , but thanks again MacG for the rescue rope …Happy Growing !!!