Dealing with heat issues in the desert...

[Rusty Trichome]

Below is what I do for my soil grow during our hot summer months in the southwestern desert. I have never grown hydro, so am unable to verify any of this for anything other than soil grows.
My flowershed is an outdoor shed approx 8' x 12' x 8' tall, of which a quarter if it is for growing. (no, it's not a metal shed)

In my humble (sometimes) opinion, "must keep temps below 80" is a guideline, especially appropriate for beginners.
-However-
Being anal about it is truly unnecessary. Ambient temps inside my outdoor growshed (2 x 400w HPS's) often reach the low 100's. This is including having the window A/C unit on 'high'.
Does it slow the growth...? Yes, a tad. Delays harvest about a week or so. However the yield is there and the quality is there.

First technique I learned
...quit hanging the thermometer by the canopy top. Was too depressing and stressful. All of my temps listed are ambient room temp, taken from the side of the grow, about 5' off the ground. I use the 'back of the hand' method of determining canopy temps. If it's not too hot for me after a minute or so, they'll be fine. (change hands often when doing this, or go around with one hand tanned, one hand not tanned)

Window A/C units.
When using a crappy window unit A/C, and it's real hot...open a vent or window, just a crack. (the higher the vent, the better) Trapped, heated air doesn't cool very well.

Never overfeed when hot.
...don't feed full-strength nutes all at once. Split it up into a couple of 'light' feedings equaling the same nute intake per week as recommended by manufacturer. Example...Instead of giving once-weekly nutes at 2 tsp per gallon, give 2 feedings at 1 tsp per gallon. (I give mine on mondays and thursdays) On the other days, I add either plain ph'd water, or micronutes, per my schedule. (Fox Farms) The strongest additive I put in the potting soil prior to use is worm castings and michorrizae fungi. I steer-clear of manures. (not so during the winter months)

Never spray with the lights on. Each drop of water sitting on the leaf acts just like a magnifying glass, and it will burn the leaf tissue. Flowering ladies prefer the lower humidity anyway. Spraying will also increase possibility of mold. You'd be amazed how long a drop of water can remain sandwiched between two leaves. Be careful watering on hot-muggy days, as it will increase your humidity levels, which can also increase chances of mold.

Ditch the intake fans unless it's hooked-up to an A/c unit.
You can add all the intake fans you want to add, and they will never work like having a strong exhaust, placed high to remove nothing but the hot air and cannabis scent. The suction caused by having the exhaust on, pulls-in the exact same quantity of air that's going out. (physics - nature abhors a vaccuum)

Stagnant air traps heat and provides no fresh oxygen or CO2.
I usually have two dedicated 'oscillating budfans' which I keep on 24/7. One on either corner of the front of the grow. Both are pointing at a slight up-angle, but one is only for the space between lamp and canopy, the other blows 'thru' the plants, providing fresh air to soil, and removing any stagnant heat. Obstructions (unnecessary shit in the room) can and will trap heat.

Lamps and plexiglass.
I don't have a cool tube set-up, but when it's just too hot at canopy top, I do hang a 3/8" plexiglass sheet horizontally above the ladies, (just below the lights) to block the direct heat from the lamp.
If nothing else works to keep the temps within 110, I break-down and raise the lights a bit. If it's still over 115, I'll shut the HID's off, and turn on some 23w CFL'S (soft white) to keep the light schedule on target. I don't know if this is a benefit, but it makes me feel better.

This is all I can think of right now, but if y'all have any questions...fell free ask.

Rusty Trichome Reviewed by Rusty Trichome on 07-27-2008. Dealing with heat issues in the desert... Below is what I do for my soil grow during our hot summer months in the southwestern desert. I have never grown hydro, so am unable to verify any of this for anything other than soil grows. My flowershed is an outdoor shed approx 8' x 12' x 8' tall, of which a quarter if it is for growing. (no, it's not a metal shed) In my humble (sometimes) opinion, "must keep temps below 80" is a guideline, especially appropriate for beginners. -However- Being anal about it is truly unnecessary. Rating: 5

[should]

Thanks for the thread rusty, ill have to try some of those techniques... its sad looking at the thermometer and seeing high 90s

[lunarose]

Rusty,

I have the same problem this time of year in my greenhouse. I have been reading about smartpots and think I'll probably give them a try next year since they are suppose to help keep the roots cooler.

Another tactic that has worked for me is to cut a piece of that weed blocker fabric with a hole in the middle for your plant and then cover it with a layer of straight perlite.

[Rusty Trichome]

Thanks for the thread rusty, ill have to try some of those techniques... its sad looking at the thermometer and seeing high 90s

My pleasure.
Keep in mind, I do not recommend anyone purposely raise the temps in their growroom to these extremes. These are methods to help keep temps reasonable enough to get quality results from a very harsh enviornment. :thumbsup:

Rusty,
I have the same problem this time of year in my greenhouse. I have been reading about smartpots and think I'll probably give them a try next year since they are suppose to help keep the roots cooler..

Would put some more thought into the SmartPots. Thoughts like...how does the pot cool the water, or at the very least, not retain ambient heat? The water will act like an insulator, collecting external heat. Or at the very least, not let the heat escape. Also, cannabis doesn't much like being fed from the bottom. At least mine didn't. (no fresh water to upper root zones, and conditions that virtually guarantee root rot in the lower root zones)

Another tactic that has worked for me is to cut a piece of that weed blocker fabric with a hole in the middle for your plant and then cover it with a layer of straight perlite.

I'm a bit doubtful the cloth and perlite are necessary, but...If it works, stick with it. A fan blowing across the pots will circulate air and should cool the roots just fine. (unless your greenhouse is sitting in the middle of an asphalt parking lot, lol)

[lunarose]

Rusty,

Thanks for the heads up on the smartpots I had posted asking about them and had not gotten any answers.

I have a nice 20" fan running in there now and that has really helped.

[Opie Yutts]

Wow, I didn't realize even growing weed in 115 degrees was even possible.

[Rusty Trichome]

Me either, till I was forced to make it work. :jointsmile:

It's not something I look forward to every year, but at least I don't panic when temps start to rise in the spring. If my wifes church friends would quit coming over unannounced, we could move the flower room indoors too, lol. Oh well...they're good people. Gotta take the good with the not so good.

We have two seasons here, (summer and winter) with two week grace periods between them. Now, I'll almost regret the cooler temps. It's actually cheaper on electricity trying to cool the flower room in summer, than it is to heat it during the winter. ($100.00 per month more during winter)

I might be doing a 4 month veg this winter, tho. If I can swing it, I'll just take my MH light out to the shed, and keep 'em on 24/7. Gotta heat the room anyways, might as well do it with HID lumens. :thumbsup:

[painretreat]

RT-thank you so much. I've been waiting to read something like this. I get snow and heat; little in between and the heat with a grow is making me nervous as heck. pr :thumbsup:

[Rusty Trichome]

My pleasure. Anything I can help with, just ask away. :thumbsup:

[darrenlayo]

Am having major heat problems myself. Only on my second grow and have just set myself up another tent for starting my seedlings and veg. I have a 1.2 x 1.2 x 2m tent laying down on its side with 4 x 200w CFL's in one shade. Couldnt believe how hot these lamps were getting but am mainly putting it down to them being self ballasting. Anyway only planted the seeds 2 days ago. When i checked the thermometer the temp had reached a maximum of 40c/104f. Hooked some decent extraction up straight away and now have it down to 33c/91f. Am growing in soil on 18/4 light and dont have any sprouters yet. Are these high temps gunna stop my seedlings from sprouting?