There are only two reasons not to use 24/0 during veg: 1) if you don't want your plants to grow too quickly (because your flowering room/cab isn't ready yet, or whatever); and 2) if your cabinet lacks adequate enough ventilation to keep the temps from getting too high if you run the lights constantly. Having the lights on 24 hours a day doesn't cause hermies, and using 18/6 doesn't produce more females. The plants do not need a dark period to 'rest up' or anything during veg.

I have tested this, because even though the book I read was clear enough about this, I had seen others say that 18/6 is better and such. So, I put some plants in one cabinet running the lights 24/0 and the same exact strain in another exactly identical cabinet running the lights 18/6. In the end, the plants that had had the lights on 24/0 were significantly larger, had more nodes, and were in general much further along than the 18/6 plants after a month. Of course, HEAT does produce more hermies and can affect the male/female ratios, and heat does build up when you run the lights constantly, so I made sure I had adequate ventilation and temps in both cabs, to rule out heat as a factor. The result: 24/0 consistently produces larger and more robust plants than 18/6. But don't take my word for it; try it yourself and you will see this to be true.

One thing that *is* important is that whatever light cycle you choose during veg, whether it's 18/6, 24/0, 16/8, whatever: don't vary it, as that *can* cause hermies. If you start with 24/0, stay with 24/0. Whatever you start with, stay with it.
jamstigator Reviewed by jamstigator on . lighting question i hurd a rumor that when your growing indoor plants its smart to keep the lights on them 24/7. is that true?? Rating: 5