Humidity and mold question

Across the board everything I read says to keep the humidity at 40% or less during flowering to prevent moldy buds. The general rule of thumb is that mold doesn’t grow in RH less than 55%. Is such low humidity recommended because the buds draw moisture from the plant itself?

From your own experience what humidity levels do you actually maintain during flowering and have you ever had moldy buds at a certain RH? Thanks.


60 rh is my hard oh shit number for the high side.

I keep them 60 or 70 in early flower and walk that down to 50 by week 3 of fliwer. I can ocasionally get to the 40s but impossible to hold that on water and feed days in my setup.

Thats my experience.

1 Like

I live in the desert and have refrigerated AC, I never see more than 35RH running 2 humidifiers in the room the tents are in, never seen moldy buds in my life.

1 Like

@smokysmurf I’m in the desert like @Hellraiser I have to run humidifiers to get the humidity up in the 40s, rarely can I get to 50% outside of monsoon season. Only time I had mold was my first grow i jarred a little too early and didn’t burp enough. But I’m sure we will see a few more folks stop through from more humid climates.

Ive never had an issue from low humidity here in the ohio valley. However, a damp towel hung in the tent will work wonders

I run 40-45% in my flowering area.

WPM actually likes, and will reproduce, in low humidity.

I run a dehumidifier during the last weeks of flower and screw the RH right down to 20%. Only had bud rot once and it was a greenhouse grow with too little air circulation

I’m in northern Humboldt. Doing Super Skunk and GDP outdoors. I have the perfect daytime climate (high 60’s to low 80’s and 50%RH). However the nights are in the 50’s and the humidity spikes to 85-90%. Am I doomed during the flowering stage?

3 posts were split to a new topic: Is this mold on my plant?