Humidity during Flowering...

[lampost]

Well, I know lower humidity is ideal for flowering... I've read about 20-30% RH is ideal.

I thought I would be all set because I live in a semi-arid climate and my humidity through veg was about 20-25%. Well now that these plants are big and transpiring they're kicking out a lot of water! I think it's about 45-55% RH now.

When do you start having to worry about problems with mold?

lampost Reviewed by lampost on 03-03-2010. Humidity during Flowering... Well, I know lower humidity is ideal for flowering... I've read about 20-30% RH is ideal. I thought I would be all set because I live in a semi-arid climate and my humidity through veg was about 20-25%. Well now that these plants are big and transpiring they're kicking out a lot of water! I think it's about 45-55% RH now. When do you start having to worry about problems with mold? Rating: 5

[cigarettes42]

you should be ok if your plants arent cramped touching eachother and that you have great air circulation. keep the air moving. also check your plants thourough and see if you see any white powdery blotches. if i were you i would pick up a bottle of serenade to keep handy. once you see just a small patch of mold then hit it with that stuff or else that little patch will spread like wildfire.

[lampost]

Thank you. I will keep the Serenade in mind as I think a few different local shops have it.

Unfortunately my plants are very cramped! I already keep my circulation fan on 24/7 but I will probably keep the oscillating direct fan on 24/7 too. I think I'm going to get a second circulation fan.

It's kind of odd though as humidity readings throughout my house are 45-50% and it's supposed to be 29% outside. Maybe I need to upgrade my meter as it's like 5 years old...

[redtails]

No that's normal, inside is usually more humid than outside here as well. That is if you don't have your A/C running a lot, they kill humidity pretty quickly.

[lampost]

Thanks I didn't know that... at least I didn't think it be that big a difference. My meter seemed to be working. I put it outside for 1-2 minutes and it already dropped from like 46% to 36%.

I'm bummed that my humidity is this high. I was looking forward to the local climate making it easy to achieve ideal flowering conditions...

I don't think the fan is going to help because it seems it's already equalizing the air in the growroom with the rest of the house. I may get a $25 inline fan and pull air in from the outside... even though it'll really cool the basement down... maybe I can just run it for an hour a day to drop the humidity outside of the growroom... thereby effectively reducing the humidity inside the GR...

I know my watering practice is compounding the problem. I have several different strains going that are 1 week apart in age so I'm watering different plants on different days... almost every day I water at least 1 plant. It's made it nearly impossible to eliminate fungus gnats, but I only see a few each day, I kill them, and then there's none to be found... so I don't think those fuckers are gonna be a problem. If I could get them all watered on one day I think that would help too..

[lampost]

Looks like it was only 43-46% tonight... didn't water today. I'm definitely going to have to try to consolidate my watering to a couple days a week....

Hey, also is direct air blowing on the plants 24/7 bad for them in any way?? I didn't want to have to do this because it seems like undue stress on the plants, but I'd rather not have to deal with any powdery mildew or budrot!! It's obviously oscillating, but I'm going to run it 24/7. I guess it's a retarded question... I mean plants are obviously fine outside with probably a lot stronger wind!! I get so anal about this shit mang!!!

[pappabear]

You didn't mention if you have an exhaust fan to vent the humid air, if you don't have one, get one. I use "go nats" for my nat problem. And thanks, I didn't know about serenade.

Remember, unless you are using CO2 your babies need fresh air and plenty of ventilation. I've heard that you can also burn sulfer to address PM and mold issues, a buddy of mine swears by this method.

oh, and yes, plants can become wind burned!!

[DreadedHermie]

Lampost, IMO bringing in outside air just to "dehumidify" your grow is probably a bad idea unless you have state-of-the-art filtration.

55% RH ain't that bad. And it's relative. Hot air can hold a lot more water than cooler air. So you need to look at your RH both lights-on, and lights-off--at your temperature extremes.

This "dry" air you're considering bringing in from outside: what's its temperature? If it's warm enough, it could actually be holding more water than cooler air whose relative humidity is higher. (The cooler air is nearer its "dew point.")

When you're talking about relative humidity, temperature is kinda what it's "relative" to. Gotta consider temp and RH together.

For air circulation, I like a few $5 computer fans in amongst the plants. Run them with cheap wall warts or a DC fan controller ($20-40) to just keep the air moving across / around the leaf surfaces to facilitate O2 / CO2 exchange. At some point in trichome development you may want to stop blowing the leaves so hard that they grind each other's trichs off. :thumbsup:

[lampost]

Lampost, IMO bringing in outside air just to "dehumidify" your grow is probably a bad idea unless you have state-of-the-art filtration.

55% RH ain't that bad. And it's relative. Hot air can hold a lot more water than cooler air. So you need to look at your RH both lights-on, and lights-off--at your temperature extremes.

This "dry" air you're considering bringing in from outside: what's its temperature? If it's warm enough, it could actually be holding more water than cooler air whose relative humidity is higher. (The cooler air is nearer its "dew point.")

When you're talking about relative humidity, temperature is kinda what it's "relative" to. Gotta consider temp and RH together.

For air circulation, I like a few $5 computer fans in amongst the plants. Run them with cheap wall warts or a DC fan controller ($20-40) to just keep the air moving across / around the leaf surfaces to facilitate O2 / CO2 exchange. At some point in trichome development you may want to stop blowing the leaves so hard that they grind each other's trichs off. :thumbsup:

Thanks! That makes me feel a little better!

I'm ranging now from about 40-50% and temps are 58-72... which is pretty low temps so I think that's good.

I would've always assumed Powdery Mildew thrived in a warm, wet environment. Is that true? I was reading a lot of conflicting info and several sources said that Powdery Mildew actually thrived in cold and wet conditions... I think Cervantes's book says that too... but isn't that guy full often full of shit!?