Is there optimal amount of light that you can give for photoperiod plants? 18/6 to 24 hours? And when to swap?

Blossom21

Blossom21

Active Member
Just like thhe title says, how much light would be the optiomal in the start to start growing for photoperiods, or is there such thing?

I've always used 18/6, but i've seen people using 20/4 or even 24 hours at the start. I'm already at the second week with 18/6 and they seem to be at least growing. But would giving more light give better results?

And if you give more light, when should you swap to 18/6 OR should i even run them higher for the full veg state? Shouldn't veg state always have 18/6 cycle with photoperiods or is my info incorrect (haven't read or studied growing much in a looong time), at least autos are different but i haven't grown in a while and never grown autos, so i don't know about them.

One thing i read that 18/6 is much better and gives you better root mass, less stress overall (breathing room to plants) and even swaps your plants faster to flowering. But that is a lttle bit bro science, but several people have said the same in some forum threads. So is 18/6 the king of lighting schedule? :D

And if you give your plants more light, does different states of germination matter until flowrering? Like should i be swapping the lighting schedule sooner than flowering state or veg state (if i go with more light)?

I have a couple indoor grows successfully done in the past (this is my third) with the 18/6 until flowering state, but i just want to know more about this topic if this is the right place to ask.

For curiosity, have anyone here done testing about this certain topic, if we leave out autos and just talk about photos? Thanks!
 
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T.H.Cammo

Well-Known Member
The information you are asking for is somewhat debatable and very much a matter of personal preference. Regarding your use of the word "optimal" in the title; do you mean optimal for the plant - or optimal to achieve whatever you are trying to achieve? My point is; there's more than one way to skin a cat.
 
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Delps8

Well-Known Member
Blossom21 said:
Just like thhe title says, how much light would be the optiomal in the start to start growing for photoperiods, or is there such thing?

I've always used 18/6, but i've seen people using 20/4 or even 24 hours at the start. I'm already at the second week with 18/6 and they seem to be at least growing. But would giving more light give better results?

And if you give more light, when should you swap to 18/6 OR should i even run them higher for the full veg state? Shouldn't veg state always have 18/6 cycle with photoperiods or is my info incorrect (haven't read or studied growing much in a looong time), at least autos are different but i haven't grown in a while and never grown autos, so i don't know about them.

One thing i read that 18/6 is much better and gives you better root mass, less stress overall (breathing room to plants) and even swaps your plants faster to flowering. But that is a lttle bit bro science, but several people have said the same in some forum threads. So is 18/6 the king of lighting schedule? :D

And if you give your plants more light, does different states of germination matter until flowrering? Like should i be swapping the lighting schedule sooner than flowering state or veg state (if i go with more light)?

I have a couple indoor grows successfully done in the past (this is my third) with the 18/6 until flowering state, but i just want to know more about this topic if this is the right place to ask.

For curiosity, have anyone here done testing about this certain topic, if we leave out autos and just talk about photos? Thanks!
Click to expand...
How much light? How much light a plant receives is referred to as the daily light integral ("DLI") and it's a function of the amount of light hitting the canopy and how long it's getting hit with that many photons (the light schedule).

Insofar as light schedule goes, Bugbee says 24/0 in veg is fine as does "The cannabis bible" (or some such). The former is a highly regarded researcher at U of Utah, the latter is a book whose author has a BS in plant science (I'm too lazy to look it up). In contrast, I've read comments from growers on a variety of sites who report that there are issues with 24/0. For me, I do 24/0 for seedlings and I vary light schedule in veg and flower (I grow autos) according to the DLI that I want to hit.

Seeing that you new to the lighting issue (pardon the pun), there's no harm in following the recommendations of the manufacturer of your light. If you want to peel the onion about what lighting is about, check out the info at growlightmeter.com. That company makes the app Photone. I don't use their software but the information they provide is first class. Get familiar with PPFD, PAR, and DLI. Check out Dr. Bruce Bugbee on YouTube. A source that was very helpful for me - Google "chandra et al cannabis". One of the hits is the Chandra paper but you can also find links to a lot of actual research.
 
Blossom21

Blossom21

Active Member
T.H.Cammo said:
The information you are asking for is somewhat debatable and very much a matter of personal preference. Regarding your use of the word "optimal" in the title; do you mean optimal for the plant - or optimal to achieve whatever you are trying to achieve? My point is; there's more than one way to skin a cat.
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Well if there has been actually been done testing for the best lighting conditions for plants before and how much they grow under different lights (if we had same lights and same setup) during their whole growth ( =meaning resulting to the biggest plant with the biggest harvest), would that be good for the whole growing community to know?

So i don't believe about personal preference in this question, let's see someone grow side by side wit 14/10, 16/8, 17/9, 18/10, 19/5, 20/4 and 24h with similar setups, don't you think the end results would be massively different? So i believe there is an "optimal range" from seed to flowering in the growing cycle how much they receive light to get the optimal growth. Like nature has it's own conditions that are always changing and still you can get massive results without basically any effort.

I understand your "preference", but that preference doesn't mean it results in optimal results, you know what i mean? I know it's simple to just have your lights under the same decades old advice, and that's perfectly fine! I'm not asking anyone else to change their preference, just my own if there is actually perfect conditions.
 
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Nutty sKunK

Nutty sKunK

Well-Known Member
When my wife was studying horticulture at Uni she shared some info with me regarding light cycles and seedling growth.

They found a 22-2 light cycle to provide the optimum growth/root establishment.

Yet to try it myself. I tend to start 24/0 then introduce a night cycle about 10 days old.

If I’m not mistaken during the night cycle Is when weed focuses mostly on developing a root structure. It was also found in a separate study that during a night cycle the plant would secrete more sugars to feed the microbial herd in the soil.

food for thought
 
Blossom21

Blossom21

Active Member
xtsho said:
!8/6 or 24/0. Just veg your plants then flip to 12/12 and flower them when you're ready.

Why worry about things and over complicate them?
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It's not that complicated if there is actual tests/data for optimal growing conditions under lights (and other things), i can just open my tent and turn a button to get light from 0 to over 500 watts. I don't think that's complicated. If there was any actual data for testing these things publicly available from reliable source (like massive cannabis growing companies, who sure have been testing things to maximize their profits), i'm sure most of the community would use them, or not.

18/6 and 12/12 has been the norm forever and has no one actually asked "if i wanted to maximize my harvest, what would be the perfect conditions just even for my lights, so my plants get the perfect amount of growth?". I'm sure it has been asked before but if such information exists, i'd want to know.
 
Blossom21

Blossom21

Active Member
Nutty sKunK said:
When my wife was studying horticulture at Uni she shared some info with me regarding light cycles and seedling growth.

They found a 22-2 light cycle to provide the optimum growth/root establishment.

Yet to try it myself. I tend to start 24/0 then introduce a night cycle about 10 days old.

If I’m not mistaken during the night cycle Is when weed focuses mostly on developing a root structure. It was also found in a separate study that during a night cycle the plant would secrete more sugars to feed the microbial herd in the soil.

food for thought
Click to expand...
That's exciting to hear, but my plants are already 2 weeks old, so testing myself is out of the question. If there's actual studies done on this (especially with cannabis), i'd like to see sources, that's what i'm looking for exactly.
 
S

Snickerpus

Active Member
Blossom21 said:
It's not that complicated if there is actual tests/data for optimal growing conditions under lights (and other things), i can just open my tent and turn a button to get light from 0 to over 500 watts. I don't think that's complicated. If there was any actual data for testing these things publicly available from reliable source (like massive cannabis growing companies, who sure have been testing things to maximize their profits), i'm sure most of the community would use them, or not.

18/6 and 12/12 has been the norm forever and has no one actually asked "if i wanted to maximize my harvest, what would be the perfect conditions just even for my lights, so my plants get the perfect amount of growth?". I'm sure it has been asked before but if such information exists, i'd want to know.
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On one side you have DLI and on the other side you have darkness hours. Now you want to veg the plants with good root growth so you set your schedule to 18/6 up to 16/8. During those 18 or 16 hours your maintain your light intensity accordingly to get your desirable DLI for veg and the 6-8 hours of dark gives you nice root growth withou triggering the plant into the flower. Once you flip to flower you crank up the intensity of your lights to get your desirable DLI for flower during those 12 hours of light and the 12 hours of dark let your plant to flower. Obviously you can veg under 24/0 or any other schedule, but you will have to keep an eye on DLI since it may overload the plant, causing minor stunting and deficiencies and less root growth. You need to proper equipment for measuring the light intensity and match it to your environment values.
 
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Delps8

Well-Known Member
Blossom21 said:
That's exciting to hear, but my plants are already 2 weeks old, so testing myself is out of the question. If there's actual studies done on this (especially with cannabis), i'd like to see sources, that's what i'm looking for exactly.
Click to expand...
How about Googling it? I bought a book on growing cannabis but all of the other information I've read and gathered has come from cannabis sites and Google.

I'd argue that there are so few studies on minute variations in lighting cycles be because plant biologists know that there's no appreciable difference and a company growing cannabis is highly unlikely to commit the resources to conduct that test. If they did take on that task, I can't imagine that they'd be too willing to share that information since it would have cost them a significant sum to ascertain.
 
B

Brandon LaDue

Member
Delps8 said:
How much light? How much light a plant receives is referred to as the daily light integral ("DLI") and it's a function of the amount of light hitting the canopy and how long it's getting hit with that many photons (the light schedule).

Insofar as light schedule goes, Bugbee says 24/0 in veg is fine as does "The cannabis bible" (or some such). The former is a highly regarded researcher at U of Utah, the latter is a book whose author has a BS in plant science (I'm too lazy to look it up). In contrast, I've read comments from growers on a variety of sites who report that there are issues with 24/0. For me, I do 24/0 for seedlings and I vary light schedule in veg and flower (I grow autos) according to the DLI that I want to hit.

Seeing that you new to the lighting issue (pardon the pun), there's no harm in following the recommendations of the manufacturer of your light. If you want to peel the onion about what lighting is about, check out the info at growlightmeter.com. That company makes the app Photone. I don't use their software but the information they provide is first class. Get familiar with PPFD, PAR, and DLI. Check out Dr. Bruce Bugbee on YouTube. A source that was very helpful for me - Google "chandra et al cannabis". One of the hits is the Chandra paper but you can also find links to a lot of actual research.
Click to expand...
I just learned about DLI recently. You said you use that with the autos. I am curious now. So if one had enough ppfd, h2o and co2. Would one be able to light the room up for less that 12 maybe even 10hrs? For the record I am not an auto grower. Just seeking info.
 
coreywebster

coreywebster

Well-Known Member
Blossom21 said:
That's exciting to hear, but my plants are already 2 weeks old, so testing myself is out of the question. If there's actual studies done on this (especially with cannabis), i'd like to see sources, that's what i'm looking for exactly.
Click to expand...
Yeah there's been plenty of people do side by side tests over the years on here and every other grow forum.
Results are varied, different people swore by different lighting regimes. But the missing ingredient was probably the DLI.
Because one guy vegging under a 400w hps had room for more light DLI wise even when at 24/0 where another guy with a 600w hps might have seen no advantage to 24/0 because he was already hitting his DLI at 20/4 schedule.

There's also evidence to show stem growth happens in dark period using energy store in lights on.

I'm sure there is an optimal light cycle but there's many elements to balance to see the real picture.

I personally have happier healthier plants with at least 4 hours dark time.
 
C

ComfortCreator

Well-Known Member
The reality is your growing skill will influence the result more than which cycle you choose. When you become really good at this, you can do any of them. The closer to 24/0 you veg the more growth you can get, but the increase from 18 to 24 is often not worth the added cost in electricity.

There are DLI limits when you are running strong and the limit is caused by the amount of CO2 in the atmosphere. That is if you do everything perfect.

Almost all experienced growers will have some dark period in veg. Think outdoors...is anybody growing in 24 hrs of strong lighting?
 
ProPheT 216

ProPheT 216

Well-Known Member
I ran 24 hrs for veg for a long time. I do 18 6 now. I feel like the plants growth stays the same, the break for resperation let's them go harder in the light when it comes back. I feel like I have seen less stretch and spacing since starting 18 6. Plants are more bushy less stretchy
 
xtsho

xtsho

Well-Known Member
Blossom21 said:
That's exciting to hear, but my plants are already 2 weeks old, so testing myself is out of the question. If there's actual studies done on this (especially with cannabis), i'd like to see sources, that's what i'm looking for exactly.
Click to expand...
Well then do your own study on your next grow and share your findings. Make sure you document everything especially the methodology used.
 
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