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.

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

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In the book
marijuana Grower's Handbook
[Indoor/Greenhouse Edition]
by Ed Rosenthal

It says:



Humidity Cannabis grows best in a mildly humid environment: a relative humidy of 40-60 percent.

can be found here:
http://www.lycaeum.org/~sky/data/mjgrowers.html

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I agree 40-60 percent

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?

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damn guys, beat me too it...

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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.

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

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i try to keep mine 55% rh in veg and low as possible in flower

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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.

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