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is 80 f too hot for cannabis seeds

How hot is to hot ?

Have you "heard or read" anything on whether or not the the sugars in the plant can actually turn to alcohol from heat? Is that possible? And if thats possible, then could the plant survive the alcohol?

Or do you just read shit and take it as gospel? Bone up on your biology there, cuz the science behind that one is flawed, Sparky.

Yeah, there are strains out there that handle higher temps than others. Introducing CO2 is most effective at around 90 deg F if I’m not mistaken.

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Have you "heard or read" anything on whether or not the the sugars in the plant can actually turn to alcohol from heat? Is that possible? And if thats possible, then could the plant survive the alcohol?

Or do you just read shit and take it as gospel? Bone up on your biology there, cuz the science behind that one is flawed, Sparky.

Yeah, there are strains out there that handle higher temps than others. Introducing CO2 is most effective at around 90 deg F if I’m not mistaken.

Wow. so much love here.

Ed Rosenthal says this:


Proper temperature is one highly variable factor. Most books state optimum grow temperature to be 70-80 degrees, but many list extenuating circumstances that allow temperatures to go higher. Assuming genetics is not a factor, marijuana plants seem to be able to absorb more light at higher temps, perhaps up to 90 degrees. High light and CO2 levels could make this go as high as 95 degrees for increased marijuana growth speed.* An optimum of 95 degrees is new data that assumes very-high light, CO2 enrichment of 1500 ppm and good regular venting to keep humidity down. It is not clear if these temperature will reduce potency in flowers. It may be a good idea to reduce temperatures once flowering has started, to preserve potency, even if it does reduce growth speed. But higher temperatures will make plants grow vegetatively much faster, by exciting the plants metabolism, assuming the required levels of CO2 and light are available, and humidity is not allowed to get too high.
With normal levels of CO2, in a well vented space, 90 degrees would seem to be the absolute max, while 85 may be closer to optimum, even with a great deal of light available. Do not let the room temperature get over 35 C (95 F) as this hurts growth. Optimal temperature is 27-30 C (80-86 F) if you have strong light with no CO2 enrichment. Less than 21 C (70 F) is too cold for good growth.
Low temperatures at night are OK down to about 60 degrees outdoors, then start to effect the growth in a big way. Mid 50’s will cause mild shock and 40’s will kill your plants with repeated exposure. Keep your plants warm, especially the roots. Elevate pots if you think the ground is sucking the heat out of the roots. This is an issue if you have a slab or other type of cold floor.
As temperature goes up, so does the ability of the air to hold water, thus reducing humidity, so a higher average temperature should reduce risk of fungus.
Contrary to many reports, high humidity is not good for plants except during germination and rooting. Lower humidity levels help the plant transpire CO2 and reduce risk of molds during flowering.
Studies indicate the potency of buds goes down as the temperature goes up, so it is important to see that the plants do not get too hot during flowering cycles. ? D. Gold: CO2, Temperature and Humidity, 1991 Edited by E. Rosenthal.

I simply typed "proper temperatures for Marijuana and CO2" in my Google Search, and Voila!

It would appear that as temps go up, THC production and efficiency seem to drop, at least according to Ed Rosenthal, who is pretty bright.

You CAN go up to 95 degrees, however, Ed feels that between 80 and 86 degrees is best (that is how I had understood it when I set my rooms up. they run at 79 to 84 degrees all the time during lights on) as above 86 degrees can see a decrease in THC content and effectiveness. Above 95 degrees at any stage and growth itself suffers. If you read carefully, you will note that he ONLY lets temps get above 86 degrees in the growth stage, never in flowering.

So. it would appear that your advice may work, thelastpirate, however,, that little bit about having higher THC levels if you don’t go above 86 degrees is pretty important, imo. And no flowering plant should ever get above 85 degrees, with or without CO2, imo, as well.

The right temperature for an optimum crop

Beginner’s Guide: the right temperature for an optimum cannabis crop

Cannabis likes a comfortable room temperature when growing indoors, or a little warmer – not too dry, not too humid. For a lot of indoor growers, that’s all you need to worry about. If you feel too hot or too cold for you in your growing zone, it is probably trop hot or too cold for your cannabis plants.

Ideal temperature for cannabis

The best temperature to grow cannabis is usually between 68-77 degrees (20-25 Celsius). If the ambient temperature around the plant drops well below 20-25 degrees, the plant’s growth will slow down and its potential yield will be inhibited or even stopped altogether. As a result, the plant never matures… It is important to note that temperature is very important during a “day” cycle, when you let your plant get light. This is when photosynthesis and growth potential kicks in. In addition, there should be no big change in temperature between day and night.

If your plant’s temperature goes above 77 degrees (25 Celsius), the plant’s metabolism will speed up. So it will then ask for additional elements: more light, more water, more carbon dioxide, and more fertilizer etc . Make sure to adjust the changes according to the temperature.

It is wise to invest not only in a thermometer, but in a thermometer attached to a ventilation or heating system, so that automatically manages the temperature in your growing room. An automatic system can also produce excellent ventilation for fresh air and to avoid carbon dioxide deficiency.

Vegetative and flowering temperature

Vegetative stage: Young growth cannabis plants in the vegetative stage prefer warmer weather than the flowering stage, in the range of 70 to 85 ° F (20-30 ° C). Learn more about the times in the vegetative phase.

Flowering phase: at the flowering stage (when the cannabis plants start to bud) it is best to keep the weather slightly cooler, around 65 to 80 ° F (18-26 ° C) to produce the best color, trichome production and smell. There should be a 10 degree difference between the night and day times for the best results. This is especially important in the flowering stage for the development of the highest quality buds.

Temperature too low

When the temperature approaches freezing, it is too cold for a cannabis plant to survive without damage. Colder weather will tend to slow growth. Temperatures below 60 ° F (15 ° C) tend to disrupt plant growth and freezing temperatures shock or even kill a cannabis plant.

Plants are more sensitive to certain types of mold when they are fresh, especially if they are also wet. Warmer weather and large fluctuations in temperature contribute to excessive leaf size and can also reduce photosynthesis.

A plant that is grown in relatively cold weather can survive, but it will never grow as quickly or as well as a plant that receives the proper temperatures. Indoor plants tend to be much more sensitive to the cold than plants grown outdoors.

Temperature too high

While cannabis plants don’t usually die of heat, temperatures that are too hot will cause plants to grow much more slowly. Note that temperatures above 26 ° C (80 ° F) in the flowering stage will not only slow bud growth, but may reduce the potency and odor of your buds. Controlling the room temperature is especially important in the flowering stage!

In heat, cannabis is also more susceptible to many problems, including mites, powdery mildew (especially if it is wet too), root rot, nutrient burning (from increased sweating of water), increased stretch, wilt caused by oxygen from the root Deprivation and reduced “odor” of the buds (as terpenes can burn at higher temperatures).


The ideal moisture in the cannabis plant environment is between 40-70%. To measure the humidity you need a hygrometer. An electric hygrometer is probably the best choice for most growers. It often has automatic features that offer more control than just moisture. Which is always good for indoor culture.

If the moisture of your plant goes below -40%, the plant will have a accelerated perspiration rate. There will be no big consequences. Your plant will simply consume water faster. As long as there is plenty of water in reserve, there is no problem. On the other hand, if the humidity is too high, your plant may have champignons, especially during the flowering period. And there, things rot very quickly . You will certainly need to dehumidify manually, in order to solve the mold problems and the consequences that result from it.

Where to measure?

The temperature must be measured at the level of the canopy and in the shade of the leaves. The canopy represents the tops of the plants, as close as possible to the lamp. The highest temperature is evaluated.

When measuring in the shade, it represents the heat of the ambient air. As we would with the weather. Here we measure the heat of the air. This measurement is made from the stomata. A stomata is a small orifice present in the epidermis of aerial organs of plants (on the underside of leaves most often). It allows gas exchange between the plant and the ambient air (oxygen, carbon dioxide, water vapor, etc.) as well as the regulation of osmotic pressure.

So we measure on the stomata of the horizontal leaves, while remaining on the upper epidermis which is directly illuminated. We note that it is from 28 / 29 ° C as the stomata begin to close. Therefore, the temperature must be below this fateful limit. And therefore on the temperature measurement where the stomata are located. That is to say in the shade of the leaves.