Ideal RH during flower?

[ShutUpDonny]

My tent grow (organic, soil, LEDs, one lonely plant - link is in my sig if you want more info) just went into flower mode a few days ago, and I'm wondering if I need to make any adjustments to RH as a result. During veg I was able to keep it at 70% by using a humidifier, but now that my girl is beginning to bud I'm thinking that 70 is too high.

I've read that lower RH encourages resin production, and obviously the higher the humidity the greater the risk of mold and other funky stuff. So my basic question is where do I want my RH to be now, and do I try to force it even lower as time goes on?

I live in a dry climate, so ambient RH in my house is in the low 50s. I'm not opposed to getting a dehumidifier either, if anyone recommends it. Any advice would be welcomed. Thanks folks!

 

[phenotyper]

Donny, I like my RH to fluctuate in flowering. For an 8 week indicated dominant I like to keep the RH from 50-65 for weeks 1-5. When they start to chunk, I try to get it around 45-50 and at the end of flower, for the last couple of weeks 35-40. Hope that gives you some guideline. I also circulate air around my plantsike crazy, helps to prevent problems at those periods with higher RH.

 

[ShutUpDonny]

Damnit pheno, you're making it real hard to +Rep you... Too much great advice. That is exactly the kind of guideline I was hoping for.

I keep an oscillating fan on her whenever the lights are on, just like the vent fan. They also come on for 15min every 2 hrs during darkness.

I can roll with my ambient humidity and a humidifier for weeks 1-5, but then it sounds like I'll need a dehuey. I assume that's what you do to get RH down into the 30s, yeah? Any particular brand or model you care to recommend?

Biggups, again and again!

 

[jagle]

ya i use a small dehumi in flowering keep the humidity 40-50%, the lower the humidity the better, no mold or fungus worries 70% is a big high.

is your meter far away from the plants, or above/below the canopy much?

 

[ShutUpDonny]

I usually keep the meter at the height of the plants, but off to the side of the tent so it doesn't get blasted by the UV from the lights. My vent fan is almost 300cfm though, so it circulates the air pretty well and there isn't too much variation when I move the meter around.

70% seemed to work really well while vegging, but I can see where it would cause problems with buds starting to develop. It hangs out at 50-55% if I just let it be, now that the radiator is on.

 

[TheIronLung317]

keep it in the mis 50's to avoid PM and mold!

 

[MakinGoo]

I like mine 40-50 but the last few weeks of flower I try 2 drop it as dry as I can get it..

 

[lightit]

i also like to keep it at 40-50% in mid to late flower, not going above 50% especially in late flower. in early flower (weeks 1-3) you would probably be fine even at 60%. but as the buds become dense they become susceptible to mold at higher humidity. i have been told that if the humidity is too low during late flower, the resin heads dry out a little and lose some of their elasticity. this keeps them from being able to stretch and swell to their full size and capacity. not sure what rh this occurs at or how substantial it is, but i thought it made sense. not really an issue for me because i cant get my rh below about 45% during late flower even with two dehueys running.

 

[putembk]

Totally agree keeping rh under 50% in flower. Because of that I never folar i spray in flower unless I have to and I let my fans run 24 hrs a day.

 

[ShutUpDonny]

Fans running 24hrs? Wow, maybe I should do that. I figured that if the lights were off then I could just circulate for 15min every few hours during darkness and be fine. Man, maybe I've been super lucky to not get PM or mold. And I doubt this helps with my damn fungus gnats either!

Does everyone else run em constantly as well? How'd I miss this?

 

[putembk]

Fans running 24hrs? Wow, maybe I should do that. I figured that if the lights were off then I could just circulate for 15min every few hours during darkness and be fine. Man, maybe I've been super lucky to not get PM or mold. And I doubt this helps with my damn fungus gnats either!

Does everyone else run em constantly as well? How'd I miss this?

If you don't already have one, get a temp/humidity gage that will give you the high and low for the last 24 hrs as well as the current readings. This will let you know how much variation occurs when the lights/fans are off. If I leave my fans off all night my temp varies about 10 degrees, however my r/h changes substantially more going over 80%. Keep in mind my flower room is only 32 sq/ft and with 5 plants in there they put a lot of moisture in the room. I don't think a larger room would be effected as much.