10/14 on/off hrs works best for High Sativa hybrids and Equatorial land race.
Id stick to 12/12 for Indica hybrids
But you could make the switch from 18/6 to 12/12 gradually like natural day length if you’re concerned about indoor light stress.
Edit: DJ Short recommends 11/13 for all plants grown from his seeds, supposedly brings out the finer sativa traits. It will shorten the flower time/yield.
I think they were hybridsthe strains tested were indica though?
I stumbled on it purely by accident. I thought I'd set the timer to 12/12 but I had done 14/10. I didn't notice for 5 weeks and quickly switched it to 12/12. The things I noticed is that the plants stretched slowly so the stems got thicker and when the buds were thickening up, they didn't collapse at all. I continue to feed with veg nutrients until buds are set so I hadn't realised I'd still been feeding them high nitrogen for 5 weeks. The last 5 weeks those buds got seriously chunky and stank out my house and neighbourhood haha. I use this method every grow now!In the end all this will have people so confused with it that they will go back to 12/12...
@easty what made you try the 14/10 in the first 5 and what do you think is the contribution of this method to the yield? Im curious to hear. So many lighting methods its becoming an art to set a timer...been using the GLR lately for veg with good success.
Interesting, never done this but it calls for an experiment.thanks easty and boris. here's a link to the study:
https://www.mdpi.com/2223-7747/12/5/1061
there is a graph that shows that the differences between flower mass and cannabinoid levels are greatest at 10 hours, which suggests the most potency
however, they ultimately conclude that 14 hours full stop is bad for thc levels (reduced by 2/5) yet great for cbd
BUT, 14 hours for 4 weeks followed by or preceded by either 12 or 10 hours for the other 4 weeks is optimal for high thc varieties
this is because although hindu kush didn't show any difference between 12L full stop and 14L for 4 weeks then 12L or 10L for 4 weeks, under the same photoperiod the northern lights had doubled the thc yield but only because of the increase in biomass (thc concentration stayed the same). it also did not matter whether the short period came first or last i.e. if the first four weeks were 10/14 or 12/12 or 14/10 or the last four weeks were
to summarize:
high cbd strain (cannatonic) has a major increase in cbd at 14L full stop, possibly even greater at higher photoperiod. high thc strains had the opposite, a decline in thc by 2/5 at 14L full stop
but, going from 14L for 4 weeks down to either 12L or 10L for the remaining 4 weeks (or vice versa) either showed no difference than straight 12L (hindu kush), or, a 50%(!) thc increase (resulting from biomass increase) in the northern lights
they recommend this to be an optimal light schedule for high thc varieties
Thanks for linking and the summary mate, I didn't have a lot of time yesterday or would've done it myself.thanks easty and boris. here's a link to the study:
https://www.mdpi.com/2223-7747/12/5/1061
there is a graph that shows that the differences between flower mass and cannabinoid levels are greatest at 10 hours, which suggests the most potency
however, they ultimately conclude that 14 hours full stop is bad for thc levels (reduced by 2/5) yet great for cbd
BUT, 14 hours for 4 weeks followed by or preceded by either 12 or 10 hours for the other 4 weeks is optimal for high thc varieties
this is because although hindu kush didn't show any difference between 12L full stop and 14L for 4 weeks then 12L or 10L for 4 weeks, under the same photoperiod the northern lights had doubled the thc yield but only because of the increase in biomass (thc concentration stayed the same). it also did not matter whether the short period came first or last i.e. if the first four weeks were 10/14 or 12/12 or 14/10 or the last four weeks were
to summarize:
high cbd strain (cannatonic) has a major increase in cbd at 14L full stop, possibly even greater at higher photoperiod. high thc strains had the opposite, a decline in thc by 2/5 at 14L full stop
but, going from 14L for 4 weeks down to either 12L or 10L for the remaining 4 weeks (or vice versa) either showed no difference than straight 12L (hindu kush), or, a 50%(!) thc increase (resulting from biomass increase) in the northern lights
they recommend this to be an optimal light schedule for high thc varieties
a happy fu(k up, and also the exact same finding as the study(!)Thanks for linking and the summary mate, I didn't have a lot of time yesterday or would've done it myself.
I can say for MNS strains shark shock, Med man, Ortega, NL5/Afg and NL5/sk the 14/10 lighting schedule works well from my experience. A happy fu(K up on my part haha.
Yeah man, i was stoked when I went to chop and realised how much more bud was there! It was the smell I was getting worried about, they sure beefed that up really heavily in the last few weeks, I had two carbon filters on my exhaust and I could still smell it about 100m up the streeta happy fu(k up, and also the exact same finding as the study(!)
that really added more to the picture with the first study from the op where they didn't test for two-phase photoperiods, except for the og, where they found both an increase in quality and an increase in flower mass if raised from 10/14 to 12/12 for the last four weeks
this study further explains that the short daylight hour phase can occur at either beginning or end of the flowering cycle, which again, does make sense when going from longer day length to shorter instead of the other way around, even though possibly the same results can be found either way
i'm trying this on the next crops especially ortega and nl5/sk. maybe will try first four weeks 12/12 second four weeks 10/14 considering it's just a closet grow
will do : )Yeah man, i was stoked when I went to chop and realised how much more bud was there! It was the smell I was getting worried about, they sure beefed that up really heavily in the last few weeks, I had two carbon filters on my exhaust and I could still smell it about 100m up the street
Please keep me posted on your grow mate, I'm very keen to see what your results are, this kind of thing always fascinates me! Best of wishes for the grow