highchome Posted June 13, 2019 Share Posted June 13, 2019 I've seen several people here and other forums arguing about 18/6 vs 24/0. From the bit of reading I've done it seems like this is not clear cut one way or the other. It seems like the idea that a dark period is beneficial comes from two things. Firstly the idea that plants need "rest" just as we would, however this is rather unconvincing as plants are not animals and anthropomorphism is not a convincing argument in general. Secondly plants apparently have a "dark cycle" however it seems like this just means that there are things that can happen without light, not that darkness is actually required. Which as I understand it means that the pros/cons are 18/6 Pro: does no harm to veg stage Pro: 25% less electricity Con: potentially slower growth than 24/0 (but to what extent?) 24/0 Pro: does no harm to veg stage Pro: potentially faster growth Con: more electricity So it seems like the decision mainly comes down to electricity usage. Given the cost of electricity a 25% reduction in usage could be significant and make this an easy choice. Does anyone have any articles/studies/papers etc that discuss this? People tend to be quite adamant that one way is clearly better than the other... It would be great to have some concrete facts or alternative just to know that for now it is debatable and both ways are entirely valid. (Having said that, I'm now considering switching to 18/6 ) Some references The Cannabis Grow Bible 4th edition - argues for 24/0 https://www.420magazine.com/community/threads/18-6-vs-24-0-the-science.425165/ - mostly pro 24/0 https://www.cocoforcannabis.com/cannabis-light-cycle-fundamentals-24-0-18-6-and-12-12/ - pro 18/6 (and fairly convincing I think) 1 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted June 13, 2019 Share Posted June 13, 2019 Read up about C3/4 plants and how darkness affects the photosynthetic process. Some plants need the darkness to complete their growth cycle. Others don't. Quote Link to comment Share on other sites More sharing options...
SkunkPharm Posted June 13, 2019 Share Posted June 13, 2019 This is why I like to grow photoperiod plants the I don't have to worry about this. I have however grown some plants during vegetative cycle 24/0. And no I harm was done.Sent from my VTR-L09 using Tapatalk Quote Link to comment Share on other sites More sharing options...
greenkush Posted June 13, 2019 Share Posted June 13, 2019 16 minutes ago, highchome said: I've seen several people here and other forums arguing about 18/6 vs 24/0. From the bit of reading I've done it seems like this is not clear cut one way or the other. It seems like the idea that a dark period is beneficial comes from two things. Firstly the idea that plants need "rest" just as we would, however this is rather unconvincing as plants are not animals and anthropomorphism is not a convincing argument in general. Secondly plants apparently have a "dark cycle" however it seems like this just means that there are things that can happen without light, not that darkness is actually required. Which as I understand it means that the pros/cons are 18/6 Pro: does no harm to veg stage Pro: 25% less electricity Con: potentially slower growth than 24/0 (but to what extent?) 24/0 Pro: does no harm to veg stage Pro: potentially faster growth Con: more electricity So it seems like the decision mainly comes down to electricity usage. Given the cost of electricity a 25% reduction in usage could be significant and make this an easy choice. Does anyone have any articles/studies/papers etc that discuss this? People tend to be quite adamant that one way is clearly better than the other... It would be great to have some concrete facts or alternative just to know that for now it is debatable and both ways are entirely valid. (Having said that, I'm now considering switching to 18/6 ) Some references The Cannabis Grow Bible 4th edition - argues for 24/0 https://www.420magazine.com/community/threads/18-6-vs-24-0-the-science.425165/ - mostly pro 24/0 https://www.cocoforcannabis.com/cannabis-light-cycle-fundamentals-24-0-18-6-and-12-12/ - pro 18/6 (and fairly convincing I think) I know many people who veg under 24/0, personally I don't because I've yet to see any meaningful speed growth. Allowing the plants some down time is also good. Personally I do 18 /6 have for many years and don't plan to switch. 1 1 Quote Link to comment Share on other sites More sharing options...
highchome Posted June 13, 2019 Author Share Posted June 13, 2019 (edited) 49 minutes ago, greenkush said: I know many people who veg under 24/0, personally I don't because I've yet to see any meaningful speed growth Yeah, exactly. That is what I think it is going to come down to for me. 1 hour ago, GreenthumbHydro said: Read up about C3/4 plants and how darkness affects the photosynthetic process As I understand cannabis is C4 so this applies Quote > C4 plants can do photosynthesis even in the closed condition of stomata. This is not my area so I'm not sure I'm getting all the detail. But as above, it does not see that the 25% extra energy cost is really worth it for most growers. However I do like knowing the relative tradeoffs behind the decisions. Thanks Edited June 13, 2019 by highchome Quote Link to comment Share on other sites More sharing options...
greenkush Posted June 13, 2019 Share Posted June 13, 2019 1 minute ago, highchome said: Yeah, exactly. That is what I think it is going to come down to for me. As I understand cannabis is C4 so this applies This is not my area so I'm not sure I'm getting all the detail. But as above, it does not see that the 25% extra energy cost is really worth it for most growers. However I do like knowing the relative tradeoffs behind the decisions. Thanks Standard photo periods need down time for respiration, auto's have however adapted to climates were there is an abundance of light, a stable auto can grow under 24/0, the question really boils down to whether its worth the extended energy bill. In all honesty its very unlikely you will see a difference between the two. 1 1 Quote Link to comment Share on other sites More sharing options...
CreX Posted June 26, 2019 Share Posted June 26, 2019 There is a lot of info about plant stress. Especially going from 24/0 to 12/12. Consensus is to gradually reduce the light to 20/4, 16/8 and then flip to 12/12 This reduces the stress on the plant and in turn reduces the chance of a hermie. Growers doing the 18/6 can negate this step as the plants are used to the light cycle and the switch to bloom doesn't stress them too much. That's another reason most growers prefer a 18/6. 2 Quote Link to comment Share on other sites More sharing options...
highchome Posted June 26, 2019 Author Share Posted June 26, 2019 Thanks @CreX, that is very interesting. (FWIW I've switched to 18/6 myself, I don't think I'll bother with 24/0 again) Quote Link to comment Share on other sites More sharing options...
CreX Posted June 26, 2019 Share Posted June 26, 2019 Also, running a Perpetual grow requires me to have some kind of stability, to accommodate all plant stages within my rooms It could never make sense for me to run 24 hours without an intermediate room to move to before bloom. Single run growers have much more flexibility to play with light cycles and really squeeze the most out of the plant. Note - there are many many more light schedule combos that growers use... But it's normally for a specific purpose or to study how a certain strain grows under different lighting schemes 1 Quote Link to comment Share on other sites More sharing options...
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