which is better? 24/0 or 18/6 lights

I love this discussion! It's an excellent debate, is it not? I would love to know all the factors involved. That's funny that you mentioned the reverse respiration oldmac, I'm glad you did, cause I thought the same thing when I read it. I agree with you too italiano, I bet it is different for different strains. which is why I believe the breeders should supply this info. with their strains. Logic would tell you that breeders are breeding their best performing plants in their environment, and I'm sure breeders are just like the rest of us, everybody does things a little differently. And as oldmac pointed out, befree's revelation is nothing more than pure genious! For indoor growers it would make sense to switch the light cycles to take full advantage of the excess Co2 @ night. And last but not least. My fellow Tn brother. Pimp, you too are correct this should be a sticky, and we also need a grow mod. I'm sure the right person will come along or step up to the plate. There's several members here who have the chops. thank you guys for your input, ya'll rock!:thumbsup:

After a year here, I thought of StinkyAttic as a spiritual mother to many of us. It was ironic she stopped by on Mother's Day. But from the two posts I saw that day....she gave the feeling, she was not happy with some of us (me included) as she thought she had raised us better then what she saw.

She is missed, not just for her knowledge, but for her moral guidance.
I've tried to do better and hope if she ever stops by again she won't be disappointed. Till a new "captain" grabs the rudder, I think we all have to row the boat together, we are all in the same boat...HMS Canna.com and we are all here because we love da' herb and what it can do.

And Fluid69, I too like a good discussion, not so sure about debates...they can spiral out of control easily.

On the subject of light schedules or photoperiods, you can see that we are talking about three distinctly different stages of a plants' growth. 1)rooting of cuttings 2)immature plants or vegitive state and 3) sexually mature plants or flowering. Each stage has it's own requirments and needs that need to be addressed.

Jorge Cervantes says plants can only process 16 hours of light maximum before needing to rest, and after that you are basically just wasting energy. If Cervates says it, I believe it! Also as some have said, plants have had night time for millions of years so it must serve a valid purpose. I used to run 24 hr light but switched to a 16/8 schedule and noticed my roots were much thicker and healthier and therefore my plants were more robust.

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Originally Posted by filo6942

I use 24/0, works great!

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That picture is great filo6942. Anyway, great info available here. Thanx all. Im convinced overall that 18/6 is the best way to go then.

18 hours of daylight, during vegging :thumbsup: ... I've tried several different light periods over the years, as well as other 'experiments', and the 18/6 photoperiod seems the best, overall, for our cannabis ... :smokin:

yeah I'm new grower but 24/0 seems best due to my climate, also I use the AC alot in my house because my computers make it tosty.

I just went to 12/12 hour light 2 days ago.

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Originally Posted by dejayou30

Jorge Cervantes says plants can only process 16 hours of light maximum before needing to rest, and after that you are basically just wasting energy. If Cervates says it, I believe it! Also as some have said, plants have had night time for millions of years so it must serve a valid purpose. I used to run 24 hr light but switched to a 16/8 schedule and noticed my roots were much thicker and healthier and therefore my plants were more robust.

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Hey dejayou30,

Could you (or anyone) please give me a reference to where Cervantes says this. I do not have any of his books and have not been able to find one to borrow (damn prudish library). I have done some extensive google searching and been very busy reading almost every answer from Jorge @ HTs dealing with photoperiod. I'm not lookin' to disagree, just would like to see and read it in context.

The reason I'm so interested in this; there is some thought that a 16hr photoperiod may be an advantage in both veggative and flower growth.

A mj plants ability to flower or not to flower is not determined by the length of the photoperiod but by the length of the dark period.
So during the vegative phase 4 hrs of dark is more then sufficent to keep it vegging and a 16hr photoperiod coupled to that gives us a 20 hr day. So using a 20hr day for 6 days gives you 1 weeks' worth of growth. (on the 7th day he rested) Depending on how many weeks you are vegging your plant you shorten the time to veg by 1 day per week.
During the flowering phase a 16hr photoperiod coupled with 8 hrs of dark time it is sufficent to keep a plant in the flower stage (might not be able to initiate flowering at only 8hrs of dark) This 16hr photoperiod would allow the plant to recieve and process light for maxium flower growth by getting 25% more light every day. This might translate to quicker finishing times for buds. This is an experiment just waiting to happen, and I will get to it one day, maybe when I retire. lol

Its from the book Marijuana Horticulture: The Indoor/Outdoor Medical Grow Bible on page 175 in the "Light, Lamps, and Electricity" section. It says:

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"Some growers leave the HID on 24 hours a day. Marijuana can efficiently process 16-18 hours of light per day, after which it reaches a point of diminishing returns, and the electricty is wasted. (See Chapter 16 Breeding)

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However, I didn't find anything further in Chapter 16, so who knows? :wtf: It does go on to say:

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I talked with Canadian and Dutch growers who claim their plants flower under a 6 hour dark and 12 hour light photoperiod. This expedited, 18 hour photoperiod regimen is supposed to work, but I'm not sold on it. Growers say that their harvest is undiminished, and that they are getting 25 percent more marijuana in the same time. I have not visited their grow rooms to verify these claims. No electricity is saved by adoption this regiment.

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So yeah, IDK. :jointsmile:

Thanks a bunch dejayou30 for the quick responce and including the whole quote. Have to respect Cervantes' opinon, tho I'm not so sure it's gospel.

The second quote is even more interesting to me, it is the shortened day routine I was talking about in my last post.

Yup, I see an experiment comming sooner rather then later. Or if anyone has used the "short day" method, how about sharing your results.

Thnx again dejayou30.

No clue if your still watching, but yes I have played with the length of days for my plants during bloom. I only tried lengthening the days and running 18/12. I got unbelievable growth that grew me out of hearth and home and the length of bloom was longer. The plants have a clock going somewhere and they were counting their bloom cycle by that light. I actually only did this once because the plants were just too freaking big, totally screwed up my grow.

I can certainly see where 12/6 might speed up the speed of bloom by tricking the plant into thinking the calendar is flying by. The only concern I have is the 6 hour night. The hormones that handle bloom need a certain length of dark and I am pretty certain 6 won't cut it.

A 6 hr dark period may not be enough to hold a plant in flower, usually it needs 8 hrs or so to stay in flower. With alot of strains tho they won't trigger flowering at 8 hrs, it may be necessary to start at 12 hrs of dark to get them to flower but you can then cut them back to 8 hrs or so after that.

While the plant does not have a clock per se, it takes a certian amount of time for certain hormones to increase or decrease, depending on light or dark duration. The plant's hormones act like switches, turning on or off certian processes such as when to go into flower mode. This is determined by the plant during the dark period.

You'll come across some recomendations of put your vegging plants into 24-36 hrs of darkeness before going to flower, this is to insure flowering and supposedly helps put the plant to flower quicker.

The photoperiod controls the rate of growth as you have seen yourself. In simple terms the more light, either intensity or duration will increase growth rates.

But everyone needs to keep in mind these are generalizations; with different strains and individual plants there will often be exceptions to general rules.

One big exception is landrace equitorial sativa's, they can veg very happily at 12/12, just because that is close to the photoperiod they are used to.

Photoperiod is one of the easiest ways to manipulate a plant and it's growth for our benefit. We are just scratching the the surface in understanding flowering btw.

hahaha maybe you guys have to step away from the keyboard and take some bong rips and focus hahaha

welcome to the boards felix. got anything interesting to add about 24/0 or 18/6? or 16/8 for that matter? or are you too busy smoking the grapes and only the grapes?


-shake

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Originally Posted by Felixthecat

hahaha maybe you guys have to step away from the keyboard and take some bong rips and focus hahaha

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you should stop smoking those male leaves and stems

:wtf:

....or stop smoking crack.

I don't think you really need the 6 hours of darkness, considering you're watering the plants, giving them nutrients, and controlling the light & temp in the room. Most proponents of the 18/6 cycle will say that during the 18 hours of light, your plants are processing the light via photosynthesis and the 6 hours of darkness allow for root growth. Considering you're controlling the environment though, root growth isn't really a huge factor unless you're growing plants so huge that they could unroot themselves from being top heavy.

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Originally Posted by Felixthecat

hahaha maybe you guys have to step away from the keyboard and take some bong rips and focus hahaha

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My first need to give negative rep, I can't believe the website actually thanked me. You are very welcome canna.com.

Excellent thread BTW, OldMac, I love the logical approach to things. Seems logic flies out the window when people see pictures of big buds in their head sometimes.

May bear stating that if you can't keep good light discipline in your veg spot that 24/0 may be your only option.

Yeah irydyum, that makes another good reason to use 24/0, falls under the enviromental issues catergory.

But I've said before the issue of 24/0 vs 18/6 or any other choice between, is a personal decision based on what works best for an individual in his or her own set up. I've used both for various reasons and now using 20/4 in one grow, just because I've got a few auto flowers in with my moms, and that was the recommendation as "best" by the seed producer. And the moms could care less (they told me).;)

*drags an old thread from the grave*

On the topic of light periods. Ive read that the best scientist is nature... Has anyone thought about what kind of effect it might have if the lights were "scaled" on and off? Like, turn a quarter of the light on at first, then slowly bring it to full lighting, like a sunrise? and vice versa obviously to introduce dark.

Maybe doing the change gradually would be easier on the plant or some such something.

Just food for thought. :jointsmile: