High temps during veg?

[BagseedSamurai]

Hempy: When you are in the 80's, what is the temps in the grow? Mine are about 10 degrees F above the ambient temps almost at all times.

 

[Iron_Lion]

This has nothing to do with sex determination but might shed some more light on the subject for the original poster. This is an article from one of the most respected names in cannabis.

Article Taken From: Cannabis Culture (Issue #13)
Written By: DJ Short
Proper ventilation and air circulation are essential to growing healthy, happy plants.

An important aspect to consider when growing plants indoors is proper ventilation, air circulation and temperature control. This practice becomes especially necessary when working with lights over 400 watts, in very small spaces, any time the temperature exceeds 32°C (90°F), or if the humidity gets too high.

The Perfect Temperature

Though sense of feel is adequate to gauge the "perfect climate" for a given plant, there is no real substitute for a thermometer and humidity gauge.

Thermometers are cheap and accurate enough for our purposes. I usually employ several thermometers in different areas in and around the grow room. Somewhere between 32-35°C (90-95°F) is the absolute highest room temperature your plants would care to tolerate. The perfect temperature would be somewhere between 24-29°C (75-85°F). Peaks of 38°C (100°F) are allowable for most strains, but not for any longer than a half hour or so. And only above the root level.

Roots and Aeration

The main area of concern involving temperature are the roots of the plants. Ideally, the roots should be kept at as constant a temperature below 21°C and above 10°C (70-50°F) as possible. The fact that warm air rises and cool air sinks works to our advantage in this case. Also, the plants end up under the larger lights by the flowering cycle, and so they're usually large enough to help shade and cool their root areas.

Still, some rooms build up sufficient heat to require a separate circulating fan, or fans, focused specifically on the root systems. A soil thermometer may be a wise investment.

Proper aeration of organic based soils is crucial in high temp/humidity areas. Perlite and vermiculite, are the tips here – add more to the soil if need be. In hydroponic systems make sure that the nutrient water temp is below 21°C (70°F). If necessary, store the reservoir outside of or below the grow room.

 

[BagseedSamurai]

Good info. Thanks Lion.

 

[guest456mpy]

Mine were about where you were until this last week when I popped for a substantially larger carbon scrubber/exhaust system. I now run 1 degree above ambient, but the damage may already be done for this cycle.

 

[OMountainMix]

Definitely higher temps can bring out some male flowers. Nobody wants to take a chance on a plant seeding itself. Unless that's what they want . . . . Lots of money in seeds if the genetics are good.

 

[!!!]

I've seen temps over 105F quite a few times indoors without a problem. Matter of fact, plants grow fast in the high heat.

Heat is a catalyst so in theory growth would be quick because photosynthesis would speed up at a higher temp. The problem in practice, as far as I know, is that stomata begin to close at 90-95F+ to prevent the plant from drying too quickly in the heat. With stomata closed, the plant doesn't get enough CO2 to photosynthesize efficiently, and so overall growth is slowed down.

That being said. This summer I vegged in 95F (35C) and I'm now flowering in 95F. I had curly leaves in veg but the plants seem OK in flower. Veg growth was much quicker and healthier when temps were in the low 80s..