Day/Night Temperatures

Has anyone ever experimented with keeping temperatures at a constant level through the whole grow?

I've been reading up, and there seems to be good reason to suspect that the recommended drop in temperature during the dark period is nothing but a myth based on the fact that with outdoor environments, nights are usually colder than day. Well, maybe they would grow even better in the wild if nights were just as warm? Besides, what's good for an outdoor grow isn't nesassarily good for an indoor grow.

I'm yet to read anyone provide a scientific basis as to why we should be dropping our temperatures at night. It just seems to be one of those things that people read everywhere and don't question it.

So the question is, has anyone actually tried this? I just got a temperature controller, and im 4 weeks into flowering and plan on keeping a constant 25c temp for the rest of the grow. I shall report back with the results. Temps at the moment range between 20 and 26.

High night time temps eat up carbos that were manufactured during the day to the process of respiration versus cellulose production. That's the science.

Me? I'd rather get fat dense colas knowing that I had given my plants a 20F drop in day to night time temps. All fruit bearing plants produce superior quality fruit with a large swing in day to night temps, especially wine grapes. I'll take a Cab that ripens with 55F temps during late ripening over one that has high night temps of say 72F.

Experiment, that's the only way you learn.

I know you are unconvinced about molasses, but maybe regular molasses usage would counter act the loss of carbs? Who knows, its fucking difficult finding good information when all these sources contradict each other.

You let them drop that low?? 20 is a pretty significant drop... Surely certain strains would react better or worse to warm/cold night temps.

How do you keep your temperatures in check? I have a temperature controller connected to a heater... it seems as though ideally, i should have another heater with another temp controller which switches on at night... Just seems a bit overkill.

see im placed in a kinda fucked situation , i live in a hot state in the south so when i flip i will have to choose if i want the 12 lights on hours to be in the day when it will be hotter to cool or the night when it will be easier. The decision is an important one because if i have them on durring the day it will be MUCH harder to cool the room , but the night temperatures will drop 10-15 degrees basically implementing that temp drop theory senior ben has up there. If i leave the lights on at night the temps will drop to about 75 ... but during the day with the lights off i fear the will go anywhere from 75+ to 85. so what to do? id like to see some better answers here so i can figure it out! good thread man!

Dro

You either grow only during the winter or use A/C.

nizmo said:

I know you are unconvinced about molasses, but maybe regular molasses usage would counter act the loss of carbs? Who knows, its fucking difficult finding good information when all these sources contradict each other.

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So you know the chemistry of molasses, and the amount, to be the same as what's produced during photosynthesis? Look, the plant manufactures its own proteins, carbos, enzymes, vitamins, etc. It does not need or really want your help. The worse gardens I see are those giving them some snake oil crap hawked by a cannabis specific vendor sold to some noob that has dreams of "big buds".

UB

Uncle Ben said:

High night time temps eat up carbos that were manufactured during the day to the process of respiration versus cellulose production. That's the science.

Me? I'd rather get fat dense colas knowing that I had given my plants a 20F drop in day to night time temps. All fruit bearing plants produce superior quality fruit with a large swing in day to night temps, especially wine grapes. I'll take a Cab that ripens with 55F temps during late ripening over one that has high night temps of say 72F.

Experiment, that's the only way you learn.

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Great info. What advice do you have for feeding times during the 12/12 cycle? I use an ebb and flow with hydroton and I currently water for 15 minutes at 6 hour intervals, the first feed time being an hour after the lights come on. Does that sound about right?

Uncle Ben said:

So you know the chemistry of molasses, and the amount, to be the same as what's produced during photosynthesis?

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I never claimed to know anything at all. I was merely suggesting a possibility based on what seemed reasonable/logical to me (which i am fully aware may be completely wrong). At the risk of going off topic, i have to say that one can not deny the fact that there are thousands of people who have successfully used molasses in their grow. It may be that the plant doesnt "need" it, and maybe they would have got the same results whether they had used it or not. I remain unconvinced on the matter in the absence of a controlled scientific study (or my own personal experience) but i am prepared to give it a go on the basis that i have not come across a single person who has reported back to say molasses ruined their crop so i feel it is not too much of a gamble, and i've decided to try it on one of my plants only... Like you say - experiment!

I research these things but unfortunately its hard to find good sources which are based on more than just anecdotal evidence. I welcome your posts because you provide more than that.

Uncle Ben said:

Look, the plant manufactures its own proteins, carbos, enzymes, vitamins, etc. It does not need or really want your help.

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I honestly mean no disrespect with what i'm about to say and maybe i am just missing the point... but of course it needs our help if we're growing indoors. I know its possible to grow start to finish without adding anything other than plain water to the soil (although im guessing it would depend on the soil)... but surely you are not suggesting that the addition of the right additives do not have a very beneficial effect on the end result? The million dollar question is - what are "the right additives"? What i do know is that you never trust a hydroponic store owner who's trying to peddle his bullshit products. I agree with you that experimenting is the best way to learn - but its a slow way.

wow so if my ambient day temp is 76 , nite should drop to ? 56 ? or u think a lil higher , they are 2 weeks into flowering 'KushBerry' , thanx in advance

nizmo said:

...and im 4 weeks into flowering and plan on keeping a constant 25c temp for the rest of the grow. I shall report back with the results. Temps at the moment range between 20 and 26.

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So how conclusive will your results be if you're starting at week 4? I think your experiment is worth doing, however, I think 25c is a little warm at night. Are you able to experiment at 22*C? That seems like a happy medium between not being hot at night and not being too cool during the day.

homebrewer said:

So how conclusive will your results be if you're starting at week 4? I think your experiment is worth doing, however, I think 25c is a little warm at night. Are you able to experiment at 22*C? That seems like a happy medium between not being hot at night and not being too cool during the day.

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Yeah i've decided to take Uncle Bens advice and lower the temperature a bit (although not as drastically as he suggests because i think i have a temperature sensitive strain). Like i said before,i don't really want to gamble on this harvest. I do agree that a constant temp is probably not the best idea (especially at 25c) and you are right - they won't be conclusive anyway because i would have been starting half way through which you would never really do. So i might just revert back to having a small gap.

I'm currently working on getting the thermostat on my heater on the correct setting - it takes a few nights of trial and error. It dropped to 16.7c last night, so ill crank it up slightly tonight and aim for about 20-22c. I'll keep day temperatures at around 25c. This growlush temperature controller doesnt seem to be very accurate. Sometimes it switches the heater on at 24c sometimes it drops to 22 before it switches it on. I set the dial to 28c (because anything lower causes the temp to drop too low before heater turns on - it sure as hell doesnt keep temps at 28c). Pretty annoying when things dont do what they say they do.

Just to make my heating situation clear;
I have a heater which i turn on at night (ill get a timer for it today) which i switch on at lights off, and then off when lights come on. I just run this using its own build in thermostat.
I then have another heater connected to this growlush temperature controller which runs during lights on which in theory keeps the temps at 25 (by setting the dial to 2. In reality, it changes between 23 and 25 because they must have cheap skated on parts or just designed it poorly but i dont think such a small fluctuation will cause harm.

I'm pretty pissed off with this growlush controller really. Its a small room and it heats up very quicky so its not like the heater turns on at the right time and then temp continues to drop until heat starts pumping - theres no reason why there should be 3 (or even 4 sometimes) degree fluctuations when using this controller.

I have a 1000 watt closet grow, temperature and humidity is constant day and night temps always stay the same. Ambient room temp is around 75 degrees with nothing running, when the 1000 watt kicks on, exhaust etc, a 9000BTU AC unit keeps temps around 75-78. I have nothing but maybe a 3-5 degree swing in temperature at all times, humidifier and dehumidifier work in constant roation to keep my room at 35%-45% humidity both day and night. I grow some nice plants with no temp swing......

Mudslide9791 said:

.... I have nothing but maybe a 3-5 degree swing in temperature at all times, ....I grow some nice plants with no temp swing......

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That is botanically incorrect. IOW, "it jest aint naturl!"

You can grow with incandescents and nights 10F higher than days.

UB

Uncle Ben said:

That is botanically incorrect. IOW, "it jest aint naturl!"

You can grow with incandescents and nights 10F higher than days.

UB

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No, it's not natural but my buds don't seem to care, much better than a drastic temp swing or a fucked up humidity swing. (shrug)

I grow better plants when the 'day' temps encourage the plants to transpire more, ie 85*.

Mudslide9791 said:

No, it's not natural but my buds don't seem to care, much better than a drastic temp swing or a fucked up humidity swing. (shrug)

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Let's see your buds, bud.

In Afghanistan, it may be a temp differential of 100F during the day, 50's at night....a 50F swing.

In Jalisco Mexico, it may be 95F during the day, 75F at night in September....a 20F differntial.

In Africa.......

Like I said, if your night time temps are running high, you've just pissed off today's carbos to respiration that would have been channeled otherwise to producing bud.

UB

DIF is the difference between night and day temps. the smaller the dif the less stretch. during veg a few degree positve dif will keep stretch to a minimun. a zero or negative dif, can cause damage, and should be monitored closely, don't mistake yellowing for a nute or ph issue, when changed back to a positive dif the plant will green back up. During veg and preflower keeping a very small positive or zero dif can very effectively limit strech, almost stopping it altogether. once preflower is over the dif should be increased in order to resume normal growth, i like it high, around +30 (im using co2 and on the extremes i go from 60 to the high 90's, i try to keep it around 90 for a high

I remember reading an article once talking about tomato yields and it said that research was showing that having a constant temperature was a great way to increase harvests

In articles that I have read recently I have learned that a smaller drop/change in temperature from day to night creates nodes that are closer together and a slightly stockier plant. This is good to know or use when using CO2 and your temperatures are into the 80's. IMO optimal temperature conditions when using CO2 and keeping low rh are 85-90 during the day (i shoot for a little less than 90 because over 90 can create stress for your babies and i want to be a little safe just in case) and 80-85 at night. So let's say 88 day and 82 night. This should create more nodes closer together, so hopefully more flowers or buds, and less green plant material (leaf, stem, ect).

Look up the thread Temps and CO2. Actually fuk it here's the link.

https://www.rollitup.org/advanced-marijuana-cultivation/402178-temps-co2.html

A recent thread here on RIU with a lot of good info on tempearatures and your plants. Should answer all of your questions. I have an article on this also if anyone still has any questions.