How cold is too cold?

[Kobayashi]

It’s freezing here, daytime temps are no more than 4 or 5 Celsius. I’ve set the plants night period to run through the day and minimum temps are around 18c, maximum about 23c in the tent. I’m going to switch to 12/12 in the next week or so there will obviously be another 6 hours without the light on. I think temps might drop to about 14-15c during the dark period with things set as they are. My exhaust fan also drops down to idle speed when the temp gets low which lets a bit of the smell out, I’d like to be able to run the temps down a little more if possible during the dark period so I could allow the fan to drag a bit more air through the filter. How low can I let the temps drop to without risking my grow? Thanks for any responses.

[Canyon Grower]

Ha, you are asking we duds still clinging to english units to do juggling in our brains ! From experience I can say that cannabis plants survive right down to 0 (centigrade). However in my grow box I dont let it drop lower than 60 (F) at night and strive for about 75(F) during light periods. So I would say, you have quite a bit of wiggle room.

[D.A.A.S.69]

Morning Kobayashi, i would think plants growing in the wild can handle lower temps much better than one's growing in tents, you should be able to tell when they are getting cold by the purple color on the stems. I would definitely go by what all the books say about the weather being to cold, like your trying to do. Good Luck with them Kobayashi.

[Dutchman1]

I believe I read somewhere below 55 degrees Fahrenheit or so cannabis plants stop photosynthesizing so no growth. Tissue damage starts around 45 to 50 F degrees If I remember correctly.Also bud rot ( Botrytis ) does best between 60 and 70 degrees F so thats another worry.

[Kobayashi]

Thanks everyone. Temps with the light on are no problem at all, I can comfortably maintain low 20’s c (70-75F ) It’s only really dark period I’m worried about. I’m growing in my garage with no proper heating so keeping it above 13-14c during the day (light off) is difficult. I think that’s around 55-60F so I think all should be ok. Thanks again.