Temperatures, Humidity

Roseman

Elite Rolling Society
The temperature is the hardest factor to take control of to me. When confined to a small space, ballasts and lights can push temperatures sky-high in no time flat. That is why I use CFLS, to avoid venting heat. This is especially true during hot summer months when outside temperature reaches its highest. Nighttime (LIGHTS OFF period) temperature can be just as difficult to regulate during cold winter month. Most gardeners are aware that temperature in the grow room plays a major role and can greatly affect the growth of plants and the quality of the finished crop. Most gardeners do not know how controlling the temperature of their garden in very specific ways they can achieve a superior crop. Drift to far from these ideal temperatures and watch your plants and crop suffer.
Before getting started it is highly recommended that every indoor garden has a max/min thermometer. (Digital $4.95 at Walmart)


This product allows the gardener to see exactly the fluctuations in temperature within their garden. Without this useful tool there is no accurate way of knowing the different temperatures between daytime (lights on) and nighttime (lights off). The difference between the two temperatures is very important to plant growth. Anymore than a 10F-15F difference between daytime and nighttime temperatures and you risk shocking and stressing the plants. You want a 10 degree difference between LIGHTS ON and LIGHTS OFF temps. In general the optimal daytime temperature for plant growth is between 70F -75F. Drift to far above this range or too far below and growth can be severely affected. Daytime temperatures exceeding 90F or under 62F and plant growth will be slowed and stunted. Plants do thrive in afganastan's 110 degrees, but they quit growing at that temp. If the temperature drifts higher than 95F the plant’s enzyme production will drop off and the plant will begin shutting down. At temperatures above 92 - 94, high photosynthesis shuts down due to the stomata in the leaves closing down to conserve water. At normal temperatures the stomata will be open, taking in CO2 and sweating water to keep the plant cool and allowing for transpiration.
Ideal temperature varies depending on whether or not CO2 is being introduced to the environment. A more suitable daytime temperature when the air is being enriched with CO2 is 80F-85F. This temperature range promotes the exchange of gases between the plants and the environment. Also, it can speed up the process of photosynthesis. Plant in an environment at 86F can perform carbon extraction from CO2 twice as fast as at 68F. It is still recommended that the nighttime temperature drop no more than 15f from that of the daytime temperature. There is another relationship between temperature and the absorbsion of gases by plants that many hobbyist growers are aware of. That is the relationship between the temperature of the water in your reservoir and the amount of oxygen the water can hold. The best range that your reservoir can be between is 60F-75F. Ideally the reservoir temperature should be at 65F because this level contains the most oxygen. Also this temperature will help control transpiration (the act of drawing up nutrients by evaporating water through out the leaves), and humidity levels. Buying a simple aquarium floating thermometer will allow you to know where you fit in this range.



$2 to $4 at Walmart, Target,
PetSmart Aquarium Dept





Another great reason for regulating the temperature in your grow room is that biological processes can be speed up exponentially by every degree. This is true for your plants as well as the potential pests that may invade your grow room.
Pests such as spider mites can reproduce up to 10 times faster with every degree the temperature rises.
These pests can destroy a garden in no time flat, you really do not want to make it any easier for them. Spider Mite Eggs and webs can screw up the buds so bad, they can nto be smoked. With a daytime temperature at a steady 72F and nighttime temperature of 65F it is much easier to control and destroy spider mite, thrip, and many other pest populations.
The same principal can be applied to the prevention and control of fungi, molds, mildews, and bacteria, which can spread more rapidly when temperatures in the grow room or reservoir exceed 90F. Also, the warmer the air, the more water it can retain which means humidity levels can easily go beyond the recommended 40-50% for Vegging. (you want high humidity for VEG, and low humidity for Flowering.) This high humidity coupled with lower nighttime temperatures can cause condensation to form on leaves. This will invite molds, mildews, fungi, and bacteria to take over you grow space. With high temperatures the likely-hood of losing control of the problem, such as powdery mildew, is very high. Once control is lost your plants may be the next to go.

Temperature is also very important when it comes to starting seeds and getting cuttings to root. Placing seedling trays on a heating mat will reduce germination time dramatically. Speeding up germination time usually leads to stronger and healthier plants. Also, less time spent between crop cycles makes a garden efficient. More harvests provided in less time can equal big bucks in the pockets of professional growers.
The ideal temperature for sprouting or cloning is 80F. Any higher and you risk burning the roots. Also, many seeds simply will not germinate at temperatures over 90F. The seeds will become dormant and never sprout.
The same principal used for seeds is used on cuttings to coax roots out quicker. The sooner cuttings can establish roots the better. If roots can be forced quickly they will grow strong and stay strong. A bottom temperature of 80F-85F, roughly 10F warmer than the air, will speed up rooting time and help to jump start those roots once they do begin. Let the temperature get too high or too low and roots growth will be hindered or they will never grow at all. Using the proper technique and the proper temperature for bottom heat not only can rooting time be speed up from 2 weeks to as little as 3 days, but the survival rate of your cuttings will drastically improve.

On the topic of roots, there is an ideal temperature for the root zone after the plants’ roots have been established. Roots are working 24 hours a day and constant attention is required concerning temperature in and around the root zone. The ideal temp for this root zone is generally 65 to 75 degrees F. At this temperature the ion exchange between the roots and the environment around them is at its absolute best. This means that the plant’s root system can take up more macro nutrients, more micro nutrients, and more oxygen at this temperature than at any other level. This makes a plant more efficient and a plant working efficiently will provide a superior yield.

Amazingly, some growers grow successfully with no themometer for the air or water. But for maximum efficiency, you got to take control of temps.

HUMIDITY? that is more simple to me. Get the Humidity VERY high for VEGGING, and very low for FLOWERING.

in Vegging, I mist them daily. I do raise the lights up, to be careful with my bulbs getting wet and breaking. And when it rains outside, it also gets cloudy and the sun's rays are blocked. Plants in outdoors, in nature do get an ocasional rain shower or thunderstorm. Do you let it rain on yours? I do, but artificially by MISTING.
AND, I bought a cheap humidifier.

Cheap Cool Mist Humidifiers from Walmart:

$26.00



Ultrasonic Humidifier With Light


$28.97



Graco, Cool Mist Humidifier, 1.5 Gallon $29.96




During Flowering, we need a low humidity, especially to avoid Bud mold and bud rot.

Cheap De-Humidifier for closets and tents
$40 at amazon.com



 

teachme101

Active Member
Just what I was looking for, THANKS..one question, I am starting some 12/12 from seed and my last sprout DIED I think because there was not enough humidity, my temps are kinda high about 80/85F I believe right now, I came home and my lights fell so it was a lil off. I checked it a few minutes ago after everything was fixed and it was at 86 not sure what humidity is right now waiting on my temp/hygrometer to come in, should get it next week. But anyways, what I did is mist some clear plastic cups and poked some holes in them and just placed them above my babies...but once they get too big for the cups..how can I keep humidity up in my box...I have 2 fans one for exhaust and one for fresh air intake....I want a homemade way of doing this...any ideas??
 

Roseman

Elite Rolling Society
Just what I was looking for, THANKS..one question, I am starting some 12/12 from seed and my last sprout DIED I think because there was not enough humidity, my temps are kinda high about 80/85F I believe right now, I came home and my lights fell so it was a lil off. I checked it a few minutes ago after everything was fixed and it was at 86 not sure what humidity is right now waiting on my temp/hygrometer to come in, should get it next week. But anyways, what I did is mist some clear plastic cups and poked some holes in them and just placed them above my babies...but once they get too big for the cups..how can I keep humidity up in my box...I have 2 fans one for exhaust and one for fresh air intake....I want a homemade way of doing this...any ideas??

I just saw a dude on here somewhere who took the clear plastic cover that held 40 blank CDs, and turned it upse\ide down over his sprouts for a DIY deal.
 

teachme101

Active Member
So I guess what I am doing is not that bad of an idea..I take the cups off when the lights are off so they can breathe. They seem to be thriving, turned the lights on when I came home from work and they had grown a little bit. My lights are a little far away right now, so there is a LITTLE stem stretch, but nothing to bad to where they are tipping over. IT IS AMAZING,....they are about 2 inches tall..and standing TALL...I covered up a bit of the stem misted the soil and that was it....hope they keep at it...Oh I'm doing a 12/12 from first sign of sprout, well after 1 day of 24hr light...didn't think they would have sprouted that fast..

THANKS MAN!
 

teachme101

Active Member
Umm...My temp with the light on about 76-80 and when the lights go out it is about 65-70, not sure on humidity I will find out in about 7 days...lol waiting on a package.
 

fatman7574

New Member
The humidity should never be really high in veg or budding states, only with seedlings and cuttings. A plant can not repire or transpire readily with high humidities.
 

fatman7574

New Member
Most experienced horticulturalists and experienced growers recommend a maximum of 40% humidity for cannibas during the day for vegging. Much less at night and during budding. There is the matter of the difference between relative humidity and humidity. I personally know of no growers actually using humidifiers at any time of growth with the possible typically just put covers over their clones to maintain humidity until the clone has developed enough roots to transpire and repire normally. Once a plant has a good root sytem high humidity just slows or prevents natural respiration and transporation.

The only time I could see a humifier being of any good use during any growth phase of a pot plant beyond the rooting stage is if you use excessive veltilation or use excessive amounts od fan circulation that causes a decline in humidity to the point that the stomata might become clogged. Myself, I think it ludicrous that a grower use fans excessively with the hopes of increasing plant strength and stem thickness as most thin stems/weakness is a result of inadequate calcium up take and fans will not correct that problem but it will cause stoma clogging quite often. Using a humifier in situations such as this is like shutting the barn door after the cow already got out. It is merely simplier to not use fans inapproprattely and not vent excessively.

I know of no other reason to use a humidifier and absolutely no reaon to maintain humidity above 40% except with new clone cuttings. Why impede a plants growth with excessive humidity or cause problems that result in too low humidity.
 

JonnyBtreed

Well-Known Member
Most experienced horticulturalists and experienced growers recommend a maximum of 40% humidity for cannibas during the day for vegging. Much less at night and during budding. There is the matter of the difference between relative humidity and humidity. I personally know of no growers actually using humidifiers at any time of growth with the possible typically just put covers over their clones to maintain humidity until the clone has developed enough roots to transpire and repire normally. Once a plant has a good root sytem high humidity just slows or prevents natural respiration and transporation.

The only time I could see a humifier being of any good use during any growth phase of a pot plant beyond the rooting stage is if you use excessive veltilation or use excessive amounts od fan circulation that causes a decline in humidity to the point that the stomata might become clogged. Myself, I think it ludicrous that a grower use fans excessively with the hopes of increasing plant strength and stem thickness as most thin stems/weakness is a result of inadequate calcium up take and fans will not correct that problem but it will cause stoma clogging quite often. Using a humifier in situations such as this is like shutting the barn door after the cow already got out. It is merely simplier to not use fans inapproprattely and not vent excessively.

I know of no other reason to use a humidifier and absolutely no reaon to maintain humidity above 40% except with new clone cuttings. Why impede a plants growth with excessive humidity or cause problems that result in too low humidity.

Where do get your information from? Are you an experienced horticulturalist?
 

JonnyBtreed

Well-Known Member
Its just funny because, being a certified Horticulturalist and Arborist, and having worked and help run a greenhouse, and having read books by both Ed Rosenthal and Jorge Cervantes, I'm curious as to why you think humidity should never be over 40% and EVERYONE else suggests 60-70% relative humidity during Vegetative growth. and 40-50% for flowering?
 

Roseman

Elite Rolling Society
Most experienced horticulturalists and experienced growers recommend a maximum of 40% humidity for cannibas during the day for vegging. Much less at night and during budding. There is the matter of the difference between relative humidity and humidity. I personally know of no growers actually using humidifiers at any time of growth with the possible typically just put covers over their clones to maintain humidity until the clone has developed enough roots to transpire and repire normally. Once a plant has a good root sytem high humidity just slows or prevents natural respiration and transporation.

The only time I could see a humifier being of any good use during any growth phase of a pot plant beyond the rooting stage is if you use excessive veltilation or use excessive amounts od fan circulation that causes a decline in humidity to the point that the stomata might become clogged. Myself, I think it ludicrous that a grower use fans excessively with the hopes of increasing plant strength and stem thickness as most thin stems/weakness is a result of inadequate calcium up take and fans will not correct that problem but it will cause stoma clogging quite often. Using a humifier in situations such as this is like shutting the barn door after the cow already got out. It is merely simplier to not use fans inapproprattely and not vent excessively.

I know of no other reason to use a humidifier and absolutely no reaon to maintain humidity above 40% except with new clone cuttings. Why impede a plants growth with excessive humidity or cause problems that result in too low humidity.

with B.S. information like that, I see why you have to put the Caveat in your signature.

I own 14 books that say strive for no less than 45% up to 55% during VEG, (higher is better)in a hydroponic or soil grow. It helps transpiration.

why is Misting recommended in VEG? Why do they make Foilage spray and sell spray bottles and humdifiers in the Hydro shops?
Of course a much lower Humidty is desired in Flowering, to avoid Bud mold.
 

JonnyBtreed

Well-Known Member
And Stomata being clogged by wind??? I think you need to go back and read your high school biology books bro....
 

MostlyCrazy

New Member
Our plants like higher humidity in veg while they are young for the same reason you start your clones in a propagator while they are still young. The plant can breath easier. If sufficient humidity is not provided the leaf will close it's pores to retain the moisture it needs. Lower humidity is required during flower to eliminate the potential of bud mold due to the structure of the bud. I go 60-70% in veg and below 50% in flower with good results.
 
Top