How cold is too cold?

[midwest420]

The "feels like" temp got down 12 this morning. Later this week we're looking at negative TEMPS which means even cooler "feels like" temps. I'm in a 4x2 tent, the bottom floor temps were 66, back wall temps were 65 and my soil temp is 65. The tent sits in a corner with two exterior walls. I've got a heat emitter on a thermostat in the tent set to 80. I just moved my emitter down about 6 inches above the floor to heat the fabric pots up a bit. I guess what I'm trying to ask is...what is too cold generally? I know genetics play a big roll, just looking for a ballpark figure. Thanks!

 

[speedwell68]

I have no idea, but I am in a similar position. I misjudged what the weather was going to do and a instant cold spell shocked the plants and has set me back a week. My advice is to keep them as warm as possible and ride it out.

 

[hotrodharley]

Using LED you really need temperatures over 80 for the best results. I’ve got a little 500 watt desk heater from Amazon connected to an Inkbird thermostat. That said I’ve had plants outdoors here that have survived multiple light freezes. Meaning 30 degrees for just a couple of hours before sunrise. They can take a lot of cold. They just don’t thrive in the cold.

 

[Severed Tongue]

Best option is a heat mat with sensor and controller, very cheap, slide it under your tent, set and forget.

 

[hotrodharley]

Best option is a heat mat with sensor and controller, very cheap, slide it under your tent, set and forget.

Bottom heating only does so much but it’s a good part of a system. Leaf temperatures under LED are a big concern and bottom heating does nothing about that.

 

[Grow Monster]

Dont go under 70 if u want constant growth. How much a plant can take of the lower temps really depends on strain and other environmental conditions. They might survive but not thrive during the temp drops.

 

[coreywebster]

@Moflow is the king of growing in cold , or wrapping tents in duvets n shit.

Thinking about that, our tents must lose a fair bit through the fabric , it's piss thin

 

[coreywebster]

I usually vent my veg tent into my flower tent to add warmth in flower .

 

[Moflow]

I dont even bother with a thermometer in the tent or up in the attic anymore but it's fecken cold lol.
I must throw a thermometer in there again.
There ya go


Heatmats work for keeping the medium warm at least.
The 4 x 4 tent can go down to 12°C - ish, low 50's F. Min extraction with 12v pc fan.
I'm sure last week it was in single figures with that bad freeze.
Plants slow down but still grow.
Attic is the coldest, maybe 10 - 12°C air temps.

The tent insulation
Polystyrene sheets keep heat around the pots.

Front door

Side view.

I laugh in the face of cold.
Im just an amateur who doesn't know what hes doing..... lol
Enjoy

 

[midwest420]

I dont even bother with a thermometer in the tent or up in the attic anymore but it's fecken cold lol.
I must throw a thermometer in there again.
There ya go
View attachment 5239293

Heatmats work for keeping the medium warm at least.
The 4 x 4 tent can go down to 12°C - ish, low 50's F. Min extraction with 12v pc fan.
I'm sure last week it was in single figures with that bad freeze.
Plants slow down but still grow.
Attic is the coldest, maybe 10 - 12°C air temps.
View attachment 5239294
The tent insulation
Polystyrene sheets keep heat around the pots.
View attachment 5239300
Front door
View attachment 5239299
Side view.
View attachment 5239301
I laugh in the face of cold.
Im just an amateur who doesn't know what hes doing..... lol
Enjoy

Thanks for the info! I definitely don't know what I'm doing half the time haha!
Well I ended up finding a garden table and a bucket, moved the light up, moved the ladies up, heat emitter still low set at 80

 

[Moflow]

I definitely don't know what I'm doing have the time haha

The other half is just as bad.... lol

 

[midwest420]

The other half is just as bad.... lol

Yeah yeah good ol predictive text lol

 

[1212ham]

A couple pages I founds searching root zone temps...

Root Zone Temperature Optimization for Cannabis - rootssat

Root Zone Temperature Optimization for Cannabis Our technology increased dry weight yield between 40-270% in Cannabis across 11 different strains in open fields and greenhouses! One of the most often overlooked elements in Cannabis and general AG growing is root zone temperatures. Besides water...

rootssat.com

https://www.cannabisculture.com/content/2002/08/02/2565/

 

[midwest420]

A couple pages I founds searching root zone temps...

Root Zone Temperature Optimization for Cannabis - rootssat

Root Zone Temperature Optimization for Cannabis Our technology increased dry weight yield between 40-270% in Cannabis across 11 different strains in open fields and greenhouses! One of the most often overlooked elements in Cannabis and general AG growing is root zone temperatures. Besides water...

rootssat.com

https://www.cannabisculture.com/content/2002/08/02/2565/

Thank ya sir!

 

[midwest420]

Looks like they perked up a bit after elevating the pots! Still might insulate the 2 exposed sides of the tent if I can't keep the temp up after this severe cold spell we're about to have.

 

[HGCC]

We have a couple of sub zero days coming up as well, curious how it goes. Stuff is slow but growing, week 6-7 is looking like week 3-4, but healthy beyond that, should make it fine.

 

[LeastExpectedGrower]

What is the heater you're using? It doesn't sound like it's up to the task... If it's staying in the 60-65 range where your tent is located, you should be able to increase internal temps.

I'm using a 400w heater on an Inkbird in a room that generally is 60-65f and it has no trouble keeping my 5x3 tent so that the low is 75f when the lights are out.

 

[Tim Fox]

mine go down to 62 with lights out at night and 75 during the day lights on, I use the bedroom heater that the grow box is in to heat everything,

 

[1212ham]

I dont even bother with a thermometer in the tent or up in the attic anymore but it's fecken cold lol.
I must throw a thermometer in there again.
There ya go
View attachment 5239293

Heatmats work for keeping the medium warm at least.
Min extraction with 12v pc fan.

Reducing extraction is often the key!
It can be hard to keep heat in a tent with the often quoted, one air exchange per minute. Who the determined that's the magic number?
Situations differ but I've never seen low co2, even with very little exchange. How much air do people think a plant can consume in 60 seconds?

 

[Moflow]

Reducing extraction is often the key!
It can be hard to keep heat in a tent with the often quoted, one air exchange per minute. Who the determined that's the magic number?
Situations differ but I've never seen low co2, even with very little exchange. How much air do people think a plant can consume in 60 seconds?

Yea, 12v fan is great for extraction in the cool tent, min air exchange. I use it all yr round, no problems.
The outside temperature has risen by 10 degrees C now the cold snap is over so the plants will love it!