Humidity in Flower...Myth or Fact?

[greenmobster440]

Have our fathers lied to us about humidity in flower?

I'm flying by the skin of my teeth on this indoor summer grow. I've got a 4x8 full of budding plants and can't seem to control my humidity very well.

Been in heavy flower now for weeks and have had spikes up to almost 79% humidity in there. I've got plenty of airflow going over and under the plants but can't seem to bring that damn humidity down.

Not a ideal environment for flowering so they say but they are coming along normally.

Other than the risk of pm or bud rot are there any good things benefits to higher humidity in flower? I've read a few threads where folks tend to find a sweet spot at 70% and 70°. I know this is out of the norm but I'm open to information.

In the past I've grown in a greenhouse with super high temps and humidity. All I could do was keep air moving and hope. They flourished and I only lost a few oz to rot but the rest was just fine. However, I've never dealt with high humidity indoors during flower.

Throughout this whole flowering period my humidity has been 60+ day and night. I'm not seeing any problems and believe me I check daily..lol.

Matter fact. The big C99 has completed her flowering and will be harvested today. She withstood the humidity just fine. No pm and no bud rot found.

How bout some input on this guys. Yeah I know lower levels are what's in the text all over but is that just a preventative measure or can cannabis benefit from higher humidity in flower?

 

[Draig]

Hey, brother. IMHO I don't believe high humidity in flower has any benefits, but with adequate airflow indoors makes a big difference, as opposed to outdoors were you have rain that pools around your buds and you're dependent on the wind which can vary.

 

[yarddog]

I think the humidity matters more when the plants get wet. Indoors I don’t think it matters as much as long as you have good airflow.

 

[KGB]

The difference is airflow. Outside that can only be controlled with something like a scrog type grow. As in sure you can put a fan on a huge 7 foot plant but will it cover the surface? Nope and what it doesn’t cover will create pockets of much higher humidity.

Have I ever grown outdoors? No but I have thought about it and read a ton of sad outside stories of bud rot and in my opinion that’s what causes it. A scrog, being flat, would reduce outdoor bud rot significantly without fans because of the surface area available to the sun and wind for drying.

If I ever grow outside that’s my plan

 

[Joes grows ct]

My humidity has been like 60 ro 70 this whole grow I was worried about pm and mold but I realized I gta stop worrying about it and I have air suking in blowing out . The pots are off the ground with a 4 inch blower fan like for a carbon filter circulating . Then a oscillating fan that doesn't oscillate no more pointed torward the wall at an angle and it kind of makes a tornadoes with the filter fan and suks out top air comes in from the bottom. But for the longest time I was acting nuts thinking I'm gonna get bud rot I really doubt I will I did notice before I put the blower fan leaves that wre over lapping had condensation built up in between them now I'm good. But with ypur question I'm wondering does it affect how the buds develop in a higher humidity seems like in veg it makes them grow crazy good what about flower?. I'd be really upset to get bud rot

 

[Hippie420]

The difference is airflow. Outside that can only be controlled with something like a scrog type grow. As in sure you can put a fan on a huge 7 foot plant but will it cover the surface? Nope and what it doesn’t cover will create pockets of much higher humidity.

Have I ever grown outdoors? No but I have thought about it and read a ton of sad outside stories of bud rot and in my opinion that’s what causes it. A scrog, being flat, would reduce outdoor bud rot significantly without fans because of the surface area available to the sun and wind for drying.

If I ever grow outside that’s my plan

I'll be watching. Sounds good in theory. Maybe do a side by side grow with a scrogged plant vs. a normal one?
To my way of thinking, it would kinda be like drying a wet blanket laying on a picnic table vs. one hanging on a clothesline. True, the flat one will get more sun, but the one on the line will get more air.

 

[CrashMagnet]

There are large greenhouses that mist the plants, seedling to flower, with a mix of water and peroxide to aid in cooling. It's cheaper than A/C and the peroxide apparently reduces the chance of PM or bud rot. I haven't seen numbers for RH in that environment, but it has to be much higher than an indoor grow with decent air flow. Since they are profit oriented, I don't think they would do it if it slowed growth or otherwise reduced yield.

 

[WeedHopper]

Hey, brother. IMHO I don't believe high humidity in flower has any benefits, but with adequate airflow indoors makes a big difference, as opposed to outdoors were you have rain that pools around your buds and you're dependent on the wind which can vary.

Totally agree. Fans moving air has always worked for me to stop bud rot and PM.

 

[WeedHopper]

By the way I grew outside many times. I covered my plants with umbrellas when it rained and after the rain I blew them off good with a leaf blower. Never had bud rot.

 

[RosterMan]

By the way I grew outside many times. I covered my plants with umbrellas when it rained and after the rain I blew them off good with a leaf blower. Never had bud rot.

But you live in that Dry heat county, try living in the wet humid country.
Bud Rot is real and it will bite ya azz and kill really fast if not stopped.
I too blow dry my plants after a good shake in the early morn.
I treat for PM which will also bloom quickly over a damp plant where I am.
Bi weekly with a product that raises the PH on the leaves

 

[WeedHopper]

But you live in that Dry heat county, try living in the wet humid country.
Bud Rot is real and it will bite ya azz and kill really fast if not stopped.
I too blow dry my plants after a good shake in the early morn.
I treat for PM which will also bloom quickly over a damp plant where I am.
Bi weekly with a product that raises the PH on the leaves

Texas is definitely not dry heat brother. Did you not see the temps and humidity I posted. You can sweat standing still.
And after it rains it gets even worse.
Dallas area is definitely not Arizona.

 

[oldfogey8]

Have our fathers lied to us about humidity in flower?

I'm flying by the skin of my teeth on this indoor summer grow. I've got a 4x8 full of budding plants and can't seem to control my humidity very well.

Been in heavy flower now for weeks and have had spikes up to almost 79% humidity in there. I've got plenty of airflow going over and under the plants but can't seem to bring that damn humidity down.

Not a ideal environment for flowering so they say but they are coming along normally.

Other than the risk of pm or bud rot are there any good things benefits to higher humidity in flower? I've read a few threads where folks tend to find a sweet spot at 70% and 70°. I know this is out of the norm but I'm open to information.

In the past I've grown in a greenhouse with super high temps and humidity. All I could do was keep air moving and hope. They flourished and I only lost a few oz to rot but the rest was just fine. However, I've never dealt with high humidity indoors during flower.

Throughout this whole flowering period my humidity has been 60+ day and night. I'm not seeing any problems and believe me I check daily..lol.

Matter fact. The big C99 has completed her flowering and will be harvested today. She withstood the humidity just fine. No pm and no bud rot found.

How bout some input on this guys. Yeah I know lower levels are what's in the text all over but is that just a preventative measure or can cannabis benefit from higher humidity in flower?

View attachment 362087

I don’t have any evidence to support my gut feeling but I think both bud rot and PM result from moisture settling on the leaves and buds. I think that is more related to the dew point than RH. My understanding is that the dew point is the temperature that air is saturated with moisture and when the temperature reaches the dew point, moisture settles into any surface it touches. I am not sure how dew point is calculated but I am sure you can go back and see if the dew point was ever reached in your grow. No PM or BR probably means you didn’t reach the dew point relative to temperature. As far as the optimal RH for flower, there are vapor pressure differential charts out there that show optimal curves for maximum transpiration which means the plant is ‘breathing’ as much as possible and therefore can grow as quickly as possible.

Sorry to go on and on and sound all sciencey. I am no scientist. I just like to read about(and hopefully understand) how things work.

This is the VPD chart I think is accurate.

 

[oldfogey8]

Dew point calculator…
https://www.calculator.net/dew-poin...dewpoint=&dewpointunit=fahrenheit&x=Calculate

 

[WeedHopper]

Interesting

 

[oldfogey8]

I ballparked a couple of data points on your charts. It doesn’t look like you are reaching the dew point so moisture isn’t settling into your plants(in theory).

 

[Oldiebutagoody]

Texas is definitely not dry heat brother. Did you not see the temps and humidity I posted. You can sweat standing still.
And after it rains it gets even worse.
Dallas area is definitely not Arizona.

I do live in Arizona and my plants are in flower and humidity has been over 60-62 every morning before lights out. I have been a little concerned about it and thinking about a dehumidifier possibly, but haven't done it yet. That and the average daily temperature is finally starting to drop a little so I think I will be fine. Would not want to live in those high humidity areas. Desert of Arizona mostly dry heat is enough for me.

 

[greenmobster440]

I don’t have any evidence to support my gut feeling but I think both bud rot and PM result from moisture settling on the leaves and buds. I think that is more related to the dew point than RH. My understanding is that the dew point is the temperature that air is saturated with moisture and when the temperature reaches the dew point, moisture settles into any surface it touches. I am not sure how dew point is calculated but I am sure you can go back and see if the dew point was ever reached in your grow. No PM or BR probably means you didn’t reach the dew point relative to temperature. As far as the optimal RH for flower, there are vapor pressure differential charts out there that show optimal curves for maximum transpiration which means the plant is ‘breathing’ as much as possible and therefore can grow as quickly as possible.

Sorry to go on and on and sound all sciencey. I am no scientist. I just like to read about(and hopefully understand) how things work.

This is the VPD chart I think is accurate.View attachment 362154

Thank you for explaining and presenting this. Makes perfect sense to me and has prob answered my question. I never once found any moisture collection on leaf that was touching and doing these screens I get a lot of packed in leaf. I never even considered dew point. Thank you, now I'm off to research this more.

 

[oldfogey8]

Thank you for explaining and presenting this. Makes perfect sense to me and has prob answered my question. I never once found any moisture collection on leaf that was touching and doing these screens I get a lot of packed in leaf. I never even considered dew point. Thank you, now I'm off to research this more.

I’d be interested in your findings. As I said, that is pretty much my gut feeling on it. I am bringing my plants into my garage at night now. The garage is drier and has less of a temp drop overnight and so far the plants are dry in the morning. Before I started doing that, the plants would be saturated with dew in the morning. So far no PM or Bud Rot. I hope it works because it really is a pain in the a$$…

 

[MariJan]

I do live in Arizona and my plants are in flower and humidity has been over 60-62 every morning before lights out. I have been a little concerned about it and thinking about a dehumidifier possibly, but haven't done it yet. That and the average daily temperature is finally starting to drop a little so I think I will be fine. Would not want to live in those high humidity areas. Desert of Arizona mostly dry heat is enough for me.

You are just west if me I have the same weather. Southern NM

 

[greenmobster440]

Well, this has me pretty tickled I guess you'd say. Thank you all for the input.