40% RH Importance During Flower?

[Iguana Man]

Just wondering how critical the 40% or lower number for humidity is when in flower? Assuming a fan is running non-stop and the humidity is occasionally over 40% (say 45-47%) is that going to be of serious concern?

 

[Weaselcracker]

You have nothing to worry about at all. Running a dehumidifier I'm lucky if I can get my RH in the 60s and all is well.

 

[GrizzWald]

Strain dependant but I know that original sour diesel won't love you, unless your that way inclined, unless your humidity is over 50%, she'll herm out below 50...

 

[HizzyB]

My saying is if you can at least lower it under 60 a time or two a day you've got a good chance of Spores and nasties not being happy


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[Major PITA]

I've neverbeen able to keep my bloom room at 40% and have never had a case of mold or bud rot. As long as you keep things clean with good air movement and turnover, you should be fine.

 

[HizzyB]

I've had a GSC that would give over 32 ounces per 1000 watts and a few of he biggest colas would have rot, never had flowers so huge since or rot. Air movement is key, your absolutely right major, keep it clean!!


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[Iguana Man]

Well I took my fan off the timer fed power strip and plugged it into a wall socket once I switched to flower. Since it's running non-stop now and the closet door is always ajar, I feel comfortable with the RH levels going into the mid to occasional upper 40's.

I guess all that reading I did about 40% max is more of an ideal situation vs. necessity.

 

[Fuzzy Duck]

It is normally RH 70% plus the higher the RH the greater the risk that is ya red line area... also check ya lights off Rh as well best done before the lights are about to just come on

Bud rot spores aka Botrytis exist & float around in the air just waiting for the right conditions to grow.

If ya RH is slightly to high air purifiers work to help control stuff & some dehumidifiers come with filters which clean the air of nasty particals as well, a reusable washable type is best.

 

[Major PITA]

Well I took my fan off the timer fed power strip and plugged it into a wall socket once I switched to flower. Since it's running non-stop now and the closet door is always ajar, I feel comfortable with the RH levels going into the mid to occasional upper 40's.

I guess all that reading I did about 40% max is more of an ideal situation vs. necessity.

I use three fans:
The first circulates air in the room = always on
The second extracts air = always on (plants like fresh air even when the lights are off)
The third is a larger extraction fan for temp control = on a thermostat

The door being ajar isn't going to cause a light leak is it?

 

[Iguana Man]

The door being ajar isn't going to cause a light leak is it?

It's a closet door. And by ajar I mean at least half way open. I close the rooms main door at night just before the timer goes off. The main door has a slotted vent at the bottom about 6" high. The 3 slots face downward toward the floor on the outside of the room which allows air to be sucked out when the homes central a/c is running. Fresh air is available in the room during the dark cycle but only when the a/c kicks in. That's fairly often given it's hot as hell right now but will probably lessen as I approach harvest time in 6 weeks. I've also got a window directly opposite the closet in the room. Once I hit flower I taped some black garbage bags up on the inside to further keep light out.

I think I'm okay on the amount of ambient light that does manage to get in though.

Oh and so far the highest RH I see on the AccuRite is 46% so if anything, I was lacking RH during veg.

 

[masonman]

The only time I would worry about low RH is when temps are high with a circulation fan blowing on the canopy. This can cause her to not transpire water correctly and stress her out. Doing a google search on plant transpiration could be very enlightening. It's always good to understand how the water you add to the soil moves through the plant and how temp/RH play a vital part in that process including the absorption of CO2 through the stomata.