Is it a problem if my grow room is at 49 to 53.5 Fahrenheit (9 to 12 degrees celcius) when the lights are off?
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I’m afraid that’s too low, people normally put the lights on at night to help warming the tent and avoid the hot temperatures by day produced by the lamp. Here you can find a quick guide:
1. Seedling Stage
Seedlings and clones like high humidity levels of 65-70%
Reason: The root system is not established
High humidity levels allow water intake through leaves
Temperatures with lights on: 20-25 C° (lights off: 4-5 C° lower)
2. Vegetation Period
Humidity levels can be lowered by 5% each week (acceptable range: 40-70%)
Temperatures can be increased a little bit (no obligation)
Reason: Roots absorb more water; evaporation through leaves cools plant(s)
Temperatures with lights on: 22-28 C° (lights off: 4-5 C° lower)
3. Flowering Period
Humidity levels need to be lowered to 40-50% (extremely important)
You can get away with 55% (anything over 60% is real bad)
It’s best to slightly lower temperatures in flowering
Temperatures with lights on: 20-26 C° (avoid high temperatures)
4. Late flowering (1-2 weeks before harvest)
The following steps are no necessity, but can improve yield, flavour and appearance
Bring down humidity levels as much as you can: 30-40%
Lower daytime temperatures, and also increase the temperature difference (day/night)
Temperatures with lights on: 18-24 °C (lights off: minus 5-10 C°)
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what will happen if at lights off my temperatures in flower are around 8 to 10 degree celsius in flower? At lights on between 20 to 25 degree celsius.
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Probably start throwing hermies thats an awful low temp.
Run your lights at night for the heat right now.
Get your plants up off of the cold ground, either did air space underneath or at least 1 1/2 of styro.
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Not much other than slower growing plants with looser buds and higher susceptibility of pests & mold. But it’s not all bad - I’ve finished plenty of grows outside in sheds or unheated garages with temps similar to that at night and the plants have been fine. No herms - many cannabis plants face these types of cold temps day and night all over the world.
Just elevate them off the ground a bit so they don’t touch cold surfaces without a good 1" barrier between them and the ground, and you can try pulling the exhausting air from the bottom of the tent so it mostly sucks out the cold air at the bottom. If you have a thermostat for your exhaust fan, that helps so it won’t run constantly and will keep the warmer air from the top. The AC Infinity T# line of exhaust fans have temp & humidity control built in, which is nice.
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thats what I do already. Lights on at nigh and exhaust off when lights off at day. I am trying to avoid running an electrical heater. But maybe that will not be a good idea. Especially if it is getting more cold.
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Sometimes ya gotta.
I’m in MN along about next month I start to use auxiliary heat
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Electric heaters scare the hell out of me. We usually have a dozen or so house fires in the winter because of them.
I was thinking of using a submersible pump with a whack of hose and having a large aquarium heater running under the egg crate the pots sit on…keep the roots warm and maybe act as radiant heating? I dunno…never followed through. And a good aquarium heater uses about 100w any way…so…yeah
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I have grown in a basement where it got as cold as 15c with no problems.
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I use the tower heaters cuz they circulate.
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59 degrees would love to see that.
Especially consecutive days of it, like say a couple weeks.
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My house temps hit 59F every night as the heater is set to 68F from 7am - 7pm, then 60F overnight. My lights go off at 7pm, and my grow goes to 59F within two hours. It’s like this every winter and I have no problems. I have 6 plants in flowering right now in the middle of week 5 and they don’t seem to be suffering.
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When I was a kid my parents were…conservative with the heat.
The basement got very cold on cold winter nights but was usually fine.
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I don’t think you will have any issues. My rooms have been far colder at lights off. I’m actually putting ice on one of my plants every night now.
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Stick your fingers in that medium, im sure you’ll find its cold.
Not good on roots or growth.
But yall got your own thing going good luck, i wouldnt advise it
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you do what? explain? 
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I have began putting ice on top of the dirt at night, to get the color changes. Mark from marks seeds told me about it. I’ll take pics as the one starts to change
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I have two lights in my 2.40x1.20m. An idea would be to separate that big box in two chambers. Light would be divided but have air circulation between them. Then run one light 12 hours. Then the other 12 hours. But I think I will not manage to divide by box like that, so light would not leak the the other side???
At the moment I stopped the exhaust fan when the lights go off. I think it is not the best idea. Almost 95% humidity. I will try to run the fan sporadically on a timer now when the lights are off.
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Yeah dude. 48 is too cold unless its a landrace that’s used to high altitudes and colder wheather. Alot of strains these days grow best indoors because we can control the temps easier. I’m afriad we’ve bred alot of cannabis to a point where it cannot survive in the wild on its own. We’ve done the same thing with grapes. I bitch about it to my wine manager all the time.
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It’s a good problem. Easier to heat than it is to cool. You can try running lights at night instead of during the day. I bet most of those space heater fires were people who used them improperly and them in front of something flammable. Kerosene or propane heaters work well outdoors.
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