In Marijuana Botany Robert Connell Clarke cites a study that says twice as much THC is formed under a 12 hour photoperiod vs a 10 hour photoperiod. And that at least 10 hours of light are necessary for adequate THC production.
He also says that shorter photoperiods may cause plants to go into flowering faster. Given 10 hours of light per day a strain may take only 10 days to flower. Whereas if given 16 hour per day it may take 90 days to begin to flower.
Strange and sad how in 2017 a book written in 1979 is still the go to book for botanical information on cannabis, at least that I've found.
The 'shorter day length causing a plant to express equatorial traits' theory sounds like wishful thinking. Effects are subjective, it'd be hard to prove or disprove this. From what I understand a plants traits as far as phenotype are fixed at birth. Of course environment plays a role but it doesn't seem like a hashplant would express itself as a Thai or Columbian from an hour or two less of darkness.
There's a reason most people use 12 on 12 off. It works. I'd only go lower if I was growing a special equatorial strain that needed it. Or if I was in a hurry to force flower. I'm more interested in the other direction, 13-15 hours of light to see if the strain will still flower quickly enough..
He also says that shorter photoperiods may cause plants to go into flowering faster. Given 10 hours of light per day a strain may take only 10 days to flower. Whereas if given 16 hour per day it may take 90 days to begin to flower.
Strange and sad how in 2017 a book written in 1979 is still the go to book for botanical information on cannabis, at least that I've found.
The 'shorter day length causing a plant to express equatorial traits' theory sounds like wishful thinking. Effects are subjective, it'd be hard to prove or disprove this. From what I understand a plants traits as far as phenotype are fixed at birth. Of course environment plays a role but it doesn't seem like a hashplant would express itself as a Thai or Columbian from an hour or two less of darkness.
There's a reason most people use 12 on 12 off. It works. I'd only go lower if I was growing a special equatorial strain that needed it. Or if I was in a hurry to force flower. I'm more interested in the other direction, 13-15 hours of light to see if the strain will still flower quickly enough..
