Do Cooler Nightime Temps Affect early Maturation?

Hi everyone,
I grow in a back bedroom in a home with "central air" heating system.
I have all the vents into the room blocked.
In other words, the room receives no heat at night or at all, other than from the lights on period.
In the Fall and Winter months, the room is in the upper 50's to low 60's every night.
78 to 85 degrees with lights on.

My yields do not seem impacted by the cool nighttime temps. I average 3.5 to 4.0 zips, consistently.
(about the same in summer months)


What I have noticed is...all my plants seem to finish a week or more sooner every winter.
Not just the clones, but plants grown from seed never seem to require the suggested finish time.
I use a microscope and pull most of my plants at ALL cloudy with a couple amber trichomes.

Would the same strain grown outdoors in two different geographical locations, finish at different times in different temps?
Do cool temps promote early maturation?

I know many other botanical species are actually triggered by temperature changes, just wondering if it affects MJ.

I believe it could be from the DIF in temps, instead of your plant putting growth into stem / node elongation. How quickly does it take for the lights to warm up the temp from the 50s-60s up to the 75+? I have literature on hand but a quick explanation can be found http://en.wikipedia.org/wiki/DIF_(technique) . So I believe those first 2-3 hours of your lights being on the plants isn't putting its growth into increasing stem height and intern throughout the day puts it into the flower production possibly taking a week off of grow time? Could be wrong just a hypothesis.

My grow room temps during the winter are in the low 60's and with lights on the low 70's. With the furnace on more often, the RH is on the dry side.

The strains I've had in my flower room are new to me, but going by the supposed flower times given by the breeder, my plants are taking much longer than they should. The karamelo I'm currently harvesting took almost 10 weeks in 12/12 and the breeder stated it was a fast-finishing Indica that could finish as quickly as 6 weeks. I have one Karamelo that will probably take 13 weeks.

How much of this delayed harvest time is due to the lower temps? I don't know, but in my mind I do factor low temps in as a contributing factor.

Night time temps "should" stay within 10°F of your lights on temp. Cannabis is a strong plant and can handle cooler temps when needed but at some level it's stunting growth. Try to keep temps consistent as possible with a slight drop at night.

They call me Bunny

dudenochance said:

I believe it could be from the DIF in temps, instead of your plant putting growth into stem / node elongation. How quickly does it take for the lights to warm up the temp from the 50s-60s up to the 75+? I have literature on hand but a quick explanation can be found http://en.wikipedia.org/wiki/DIF_(technique) . So I believe those first 2-3 hours of your lights being on the plants isn't putting its growth into increasing stem height and intern throughout the day puts it into the flower production possibly taking a week off of grow time? Could be wrong just a hypothesis.

Click to expand...

It takes a couple hours to reach 75, then a few more hours to reach the point where it settles in at 80 or so for the rest of the day.
The 80-85 temps are at 6 inches below the canopy, and it is probably cooler at the base of the plants. The room itself has a thermometer, on the wall and it rarely reaches 75 as the ambient temp.
Thanks for the link.
I have exhaust fans and a passive intake. The exhaust fans are on timers as well and come on 15 minutes after the lights.

profterpen said:

Night time temps "should" stay within 10°F of your lights on temp. Cannabis is a strong plant and can handle cooler temps when needed but at some level it's stunting growth. Try to keep temps consistent as possible with a slight drop at night.

They call me Bunny

Click to expand...

And where in nature does the night time temperature remain within 10 degrees of the daytime temperature? Growth does not slow until temperature reaches about 40 degrees for an extended period.

We call you Funny

profterpen said:

Night time temps "should" stay within 10°F of your lights on temp. Cannabis is a strong plant and can handle cooler temps when needed but at some level it's stunting growth. Try to keep temps consistent as possible with a slight drop at night.

They call me Bunny

Click to expand...

I have heard that pot prefers less temp variation than some plants however...
I used to live in Northern Ca. in Marin County, just north of San Fransisco.
I grew outside in a few gorilla grows in the foothills and mountains along the coast.
Temps would reach in the 90's everyday and most nights they would drop to 65-75. Often the fog would roll in at night and not burn off until after 10:00 am.
I also grew a few plants outside last summer here in Colorado.
Same thing but with much greater variation. Temps are in the 90's everyday. (sometimes even 100)
At night it can be in the 60's or even cooler when storms roll in.
Some of the best yielding, strongest, biggest plants ever.
They went through 30+ degree temperature variation everyday.
In the fall here, you are lucky to finish in time because the temps start to get in the 40's at times.
They both finished before the frost and I have plans to grow a few more outside this year.

my room runs lights on around 82, i go in after lights out and set a/c at 66. I can run 82 because I supplement c02 and have a sealed room. If I don't turn temps down. the room gets really humid and stale.

CaretakerDad said:

And where in nature does the night time temperature remain within 10 degrees of the daytime temperature? Growth does not slow until temperature reaches about 40 degrees for an extended period.

We call you Funny

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In nature??? So your against grow lights, because no light bulb is sunlight. And I'm sure you don't use nutrient supplements at all. LST, topping, training is all not found in nature.

You can call me funny all you want, I like being funny. You can ask me all the questions you have to because obviously you need instruction. The answer I gave is for optimal conditions, which I assume the poster was looking for. And yes 10°, I'd recommend to aim for 81° average light on temp and 72° at the coolest during lights off. That is optimal temperature for cannabis. The metabolic nature of the plant wants that.

Funny Bunny

chuck estevez said:

my room runs lights on around 82, i go in after lights out and set a/c at 66. I can run 82 because I supplement c02 and have a sealed room. If I don't turn temps down. the room gets really humid and stale.

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Are you keeping your humidity between 45 and 50%? If you can lower the humidity you should be able to keep temps higher at night without getting dew. Plus no additional cooling cost.

They call me Bunny

profterpen said:

Are you keeping your humidity between 45 and 50%? If you can lower the humidity you should be able to keep temps higher at night with dew.

They call me Bunny

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Running the a/c lower with lights off keeps my humidity in check. running a dehu makes the a/c fight the dehu. and pumps up the electric bill. running the a/c lower has worked fine for 5 years.

chuck estevez said:

Running the a/c lower with lights off keeps my humidity in check. running a dehu makes the a/c fight the dehu. and pumps up the electric bill. running the a/c lower has worked fine for 5 years.

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Are you dehumidifing in the room or the room your intake air is coming from?

They call me Bunny

profterpen said:

Are you dehumidifing in the room or the room your intake air is coming from?

They call me Bunny

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I run a sealed room, NO EXHAUST. The a/c does the dehumidifying. It is a ductless. It just recirculates the air in the room and removes moisture from it as it cools.

chuck estevez said:

I run a sealed room, NO EXHAUST. The a/c does the dehumidifying. It is a ductless. It just recirculates the air in the room and removes moisture from it as it cools.

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You have no fresh air intake at all? Not even a passive intake? Your plants just continually rebreath the same air?

They call me Bunny

profterpen said:

You have no fresh air intake at all? Not even a passive intake? Your plants just continually rebreath the same air?

They call me Bunny

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YEP, they breathe the c02 i provide for them and the oxygen they produce them self. [video=youtube;4jkkCDUhpNI]http://www.youtube.com/watch?v=4jkkCDUhpNI[/video]