How do plants deal with 98 degree temps?

[Delps8]

I need help about a hot spell that's coming up in a few days.

Grow Info

Strain - AK-48
Number of Plants? 2
Growth Stage? Flower - week 2.
Plants are in good shape but have just recovered from a mild case of nute damage. I dicked up the conversion factor so I was 40% over strength for the first week of flower.

How Long? 4 sets of nodes on 7/20/17 = 36 days
Indoor or Outdoor? Indoor
Grow Type - Hydro

Reservoir Size - 35 gals capacity, 28 gals to refill to 1/2" below net pot
Reservoir Temperature - 68 degrees ± 0
Medium - Started in rock wool
Hydro Setup - RDWC

Size (Wattage) of Light? How Many? 1 600 watt LED, mfg says it draws 320 watts, KillaWatt says 400.
Light schedule - lights on/off at 8 AM and 8 PM.
Is it Air Cooled? Yes, cooled by internal fans.

Temperature of Room/Cabinet? Average high is 82±, average low is 72±.
RH - Average high about 72%, average low about 68%
PH - 5.8, has varied from 5.6 to 6.0

Pests - None known
Type and Strength of Fertilizers used? Fox Farm hydro nutes at about 60% recommended strength. Also CalMag.
Size or Square Footage of Room? 2' x 4' x 8'

Using an BlueLab monitor and have an Active Aqua water chiller. An RO unit feeds a 55 gallon cistern in the garage. The cistern temp is about 80 (August in Southern California) but the chiller brings the res down to 68 in < 6 hours.

Problem Statement

I live in SoCal and my grow tent is in a garage that is unheated and uncooled.

The weather forecast for next week is brutal - high 80's to high 90's for the entire week. The temps in the tent run about 1 degree under outside temps and the canopy temp is generally a few degrees lower than that.

What will my plants do if the tent temps get into the 90's and as high as 98 degrees?

I can put in a portable A/C but I'll have to create a plywood "door replacement" to fit in the door frame and then create a cut out for the vent. That's a fair amount of work that I'd rather avoid if I can.

I appreciate your suggestions, advice, and comments.

 

[Chris Scorpio]

I've had my tents above 90 a few times, normal is around 86-88 for me

A few days shouldn't be too bad , maybe add fans to keep air moving
If it's gonna be longer maybe do the AC unit

 

[Delps8]

Thanks for the quick reply - I prefer the "no air conditioner" approach.

 

[Spitz]

If your lights have the ability to dim, dial it back 50%. Half power will veg your plants fine for a week, the light will produce half the heat, and potentially heat stressed plans will thank you for cutting light intensity. If the RH in your garage/tent is high, 98 won't be an issue for a few days. If it's low, could be trouble.

 

[Derbybud]

Fans and maybe look at changing your light schedule to come on at 9 pm and off at 9am so the sun doesn't play as big a roll

 

[Spitz]

Question... are you cooling your reservoir water? If not, how do you keep it sterile at those temps?

Sorry, I see you are on week 2 of flower, I still think you'd get by fine cutting intensity a bit. Dial it down or raise the light a bit. Just keep a close eye on them and read/react.

 

[Delps8]

Hi folks.

Thanks for the replies.

A few hours ago, I was thinking I'd play the odds. The big factor is that weather forecasts are consistently high. Part of that is that the forecast temp is alway for a slightly different location but the other factor is that forecasts accuracy tends to drop quickly > 3 days. I can deal with a couple of days at 90+ but…

Playing the odds is looking very dicey with the latest forecasts - Sunday through Friday are 93, 100, 102, 98, 96, and 92. Ugh.

The res is chilled to 68º by an Active Aqua chiller. Runs like a champ.

The output of my LED isn't adjustable. I can raise it and I will fire up the inline fan (4" hurricane) but that won't do that much for me since the LED runs pretty cool.

Switch light schedule - if I'm on lights on between 8 AM and 8 PM what's the impact of flipping that around? I'd have to keep them off for a second 12 hour period and then fire them up at night…right?

The LED doesn't add that much to the temps (one of the reasons I chose LED) and, even with the lights off I'm looking at a temp of 102º on Tuesday.

The big question - what happens to the plant at 102? I've read that growth slows down over about 85 (not using CO2) and will stop at higher temps but at 102 will they just not grow and then recover at night, or is that temp just giving me a choice between Regular or Extra Crispy?

 

[Delps8]

I decided to not play the odds - temps are forecast to be very high. Wunderground is forecasting 96, 102, 101, 100, 100, 95, 96, and a high of only 91 on Sunday. Back out the few degrees of inaccuracy and it's at lest 90 for the next week.


Most of yesterday was spent buying and installing a Whynter_ ARC-14SH - it's a 14k portable AC. The garage is 20 x 20 so I need a good sized unit and it also has a dehumidifier and a heating function. Those will come in handy to control humidity for the rest of flower (once this hot spell passes) and, since the garage will drop into the 50's in the winter, the heater function will allow me to grow in the winter.


Had to kludge together the setup for the hoses and the window kit. A total pain in the ass but it was a last minute thing and I do like in a city where "people do not get their hands dirty" so garages have no workspaces. Anyway, per the pix, it's working and will get me through the week. I need to set up something more permanent and flexible with the exhaust hose and the outlet/venting but, once that's squared away, this setup should make things easier.


In the pix, one of the hoses is sitting on a cardboard box. That's the inlet hose that I hooked up but am not using. The AC is sitting on shelving because the hose length is limited and, since I did a res change (going into week 2 of flower!!), the chiller, visible in the lower left, is working hard to drop the temp of the new res water.


Now I've just got to figure out why I'm using so much pH Up…but that's a tale of woe for another thread.

 

[425jesse]

Good choice, high temps will slowly but surely diminish he outcome as far as smell, taste,and total frostiness. How are the temps now?

 

[Delps8]

Thanks for the info - definitely don't want any of that to happen.

AC unit's doing its thing.



Nice to get the temps and RH down.

 

[LedGuy74]

In the end you will definitely appreciate that window unit... I hated trying to deal with temps without one on hot days.. I regularly flowered in triple digits inside on my first grow. Now I have a window unit and the worst it gets is roughly 84 in the grow. Also who wants to tend to their plants in a hot ass garage.

 

[Delps8]

LedGuy74:

Wow, 100+ and they lived. Tough little bastards, eh?

"Also who wants to tend to their plants in a hot ass garage."
Very good point. I was worried about them but, yup, without the AC unit, I'd have to spend time in a hot box to take care of them.

"Better living through modern chemistry". becomes "Better living with happy plants."!

 

[LedGuy74]

Yeah actually the weather didn't bother them to much believe it or not... now the nute burn from nuking them with miracle grow thanks to lack of experience... now that took a toll but I mean overall by the time I put my plants in 12/12 the temps were a bit lower (high 80's) and they looked healthy I did veg with cfl though so they were by no means monsters but that 3 monther was decent for a first timer imo lol.. one veg'd for over three months the other three veg'd for 5-6 weeks.. after all the crap I went through and the turning them around and having them looking nice and healthy all four of them produced pollen sacks and no pistils lol ..... but I had bought a fem seed a week later and started my second grow and it was easy as hell I coasted through it pretty much...

 

[Delps8]

" all four of them produced pollen sacks and no pistils"
No kidding (can I say "no shit" on this site?)
Anyway, that sucks. Sure, you learned a lot but "Oh, by the way, the last 12 weeks of you life will result in zero grams of product. Have a nice day!"
What's the emoji for head slamming on desk?

"but I had bought a fem seed a week later and started my second grow and it was easy as hell I coasted through it pretty much..."
Glad to hear that!

There's a shit ton of learning involved here (mods - a "shit ton" is a technical word - it's in there with "short ton", "long ton", and "metric ton") so you rolled over what you'd learned and did bigger and better. Very cool.

 

[LedGuy74]

Oh yeah trust me I didn't take it well lmao. Only reason I kept going is because I had purchased an led a couple weeks before flip so I could finish them properly and I sure didn't want to just let the light go to waste.

Anyhow you are working with a nice sized personal tent how much are you looking to get out of the space? I had to start off with a 4x2x4 and whenever I move granted there is more space I'll probably buy a 4x4 for flower and use the 4x2 for veg but that's down the road for now I'm focusing on getting the most out of my 4x2. I built a cheap scrog and plan on throwing it in next grow and aiming high.

 

[Delps8]

Oh yeah trust me I didn't take it well lmao. Only reason I kept going is because I had purchased an led a couple weeks before flip so I could finish them properly and I sure didn't want to just let the light go to waste.

"didn't take it well"
I had to pull the plug on one of the plants back in about week 3 of veg. Sorta sucked but it was clearly the runt of the litter and it just didn't look "right" compared to the other two plants.

Anyhow you are working with a nice sized personal tent how much are you looking to get out of the space? I had to start off with a 4x2x4 and whenever I move granted there is more space I'll probably buy a 4x4 for flower and use the 4x2 for veg but that's down the road for now I'm focusing on getting the most out of my 4x2. I built a cheap scrog and plan on throwing it in next grow and aiming high.

I have no idea about yield. I know that it won't be as much as I'd like because there's a huge difference in size between the two plants. One plant ("Norah") has a canopy that's 42 inches while the other ("Nancy") is 30 inches. Same strain, same environment, etc. Go figure.

SCROG is the way to go! I bought a net from a company in TX but didn't use it on this grow. My workload was really heavy so I didn't make the time to do what needed to be done. I was able to top and FIM but I missed the boat on SCROG.

4 x 4 would be nice but, like you, I'm at 2 x 4 now and my plans is to do a 2 x 4 well because that should yield as much as I need for personal use.