How can root temps of 18 Celcius (64 F) affect grow?

I am curious about the effects of cold temperatures on my plants. I am growing a 70% indica 30% sativa hybrid, and I would like to hear anecdotal evidence of possible problems if the temperature during flowering stays at 18 C the entire flowering time. If I yielded 10 ounces in my grow space with 22 C (72 F), could I get substantially less yield (8 ounces? 5 ounces?) if grown at same conditions except have the temperature at 18 C? I know some nutrients are not absorbed at lower temperatures and cell metabolism drops, but I would like to hear how this has affected yields for anyone who has experienced these types of temperatures during their grow.

beepy1 said:

I am curious about the effects of cold temperatures on my plants. I am growing a 70% indica 30% sativa hybrid, and I would like to hear anecdotal evidence of possible problems if the temperature during flowering stays at 18 C the entire flowering time. If I yielded 10 ounces in my grow space with 22 C (72 F), could I get substantially less yield (8 ounces? 5 ounces?) if grown at same conditions except have the temperature at 18 C? I know some nutrients are not absorbed at lower temperatures and cell metabolism drops, but I would like to hear how this has affected yields for anyone who has experienced these types of temperatures during their grow.

Click to expand...

I've noticed slower growth and smaller yields at colder temperatures. Specifically when plants were sitting on a concrete pad in an unheated garage in the winter which is why they are now raised off the floor. It also depends on how you're growing. 18 C would be fine for DWC.

xtsho said:

I've noticed slower growth and smaller yields at colder temperatures. Specifically when plants were sitting on a concrete pad in an unheated garage in the winter which is why they are now raised off the floor. It also depends on how you're growing. 18 C would be fine for DWC.

Click to expand...

I am growing in coco. Why do you say DWC would have no problem with colder temperatures?

beepy1 said:

I am growing in coco. Why do you say DWC would have no problem with colder temperatures?

Click to expand...

The cool water is great for the roots (no root rot). I'm growing in my basement, water and air temps are 16 - 20C (60 - 68F), the girls really like it.

I grow organic,in my heated and dry walled garage-shop.I needed the space so i am growing on the floor this winter.I have 2 layers of felt paper,1 inch of foam and 1/2 inch of wood on my floor.so i don't get that frost type of cold.set heat on 61 degrees and leave it there all winter.(Temp at the soil,) lights on run an average of 68-70 and at lights off 62-64.I have not had any problems at all.they are all budding just fine.Next winter I hope to have them off the floor though.will it help any? don't know but will be easier to work with them when I can stand and do it.I keep a temp on my work tables as well and the temp there is not much difference at night than the floor only 1 degree.garage is 18 by 24 I leave the doors to the tent all the way open and just circulate the air in the tent around with 2- 8 inch fans on low ,one just above the soil the other near the top of plants. lights out the fans go off also.it can get smelly inside garage without the carbon filter running but I love the smell ( not even using one this year). No neighbors near me.I do not believe the soil it self get near as cold as the temp does at lights out.that would take more than 12 hours not sure though.not sure about plants producing heat at night that would be above my knowledge.I do know the colas seem to like it ( large and healthy ).do not have any pictures for you.hope to get some before chop in a couple of weeks and post on the t-5 site.please no trolling because I use t-5 and not led.The question was on temp not lighting and I adjust everything to what I use.Be blessed and good luck.

I plant outdoors (established plants and seed) after the first frost (usually lows in the mid 40s) and mound them with dirt and cover with straw to protect from future frosts.

Usually takes about a month til temps reach the 60s. They start slower than the indoors where I keep it low to mid 60s. I wouldn't say a lot slower but noticeable.

I'm growing in my shop, I put some half inch thick foam rubber puzzle mats down under the tent to isolate the tent from the cold concrete. Drip trays also have many protrusions on the bottom that keep an air space under the tray.