24 hours for the first week,then 20/4 or 18/6 after that.the dark period is important.the plants do some important things during the dark period.
this is the reason why plants tend to look more vibrant if they have some dark time.but you can get away with 24/0 throughout the whole of veg.
I dont know why the myth of cannabis needing a dark phase is perpetuated so much on this site, but trust me, as a biologist, the science just does not support it.
True that Dogg !!!!! Growing is a personal thing. I know a guy who SWEARS that his 21:45 light/2:15 dark schedule produces a better and bigger bud......whatever.........
I've tried both and the only difference I've found is that my plants get tighter inter node spacing on 24/0 than on 18/6.
You are always in my heart. ~RIP Muriel
First Grow (Juicy Fruit Bagseed)
However, that kind of evidence is called anecdotal evidence. You should not base your grows off of anything that is anecdotal. The scientific method is far superior, and they are thousands of hours of trial work that has shined light on this question time and time again.
Growing plants is a science. Use it to your advantage and you will be so very grateful....and stoned.