High humidity

DoobieDoobs said:

Hey guys, I hope this finds you well.

Hey guys, um these past few weeks there has been constant rain where I live. I have a cheap hygrometer and well seems like when it rains humidity inside my tent reaches around 68%, and my hygrometer has a 5% error so it is (63% , 73%). which is a too much for flower I presume.

Do you guys know a homemade remedy for high humidity? Im not sure I can afford a dehumidifier at this moment, next grow for sure tho.
Thank you!

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Hey Doobie,

I had the same problem with my last grow. I tried everything. 15x11 grow room in old basement coal scuttle, growing 4 Silver Haze in 5 gallon pots.

I ended with a 2000sq ft rated dehumidifier in the tent, three fans circulating air inside, 6”exhaust running and portable AC outside the tent. I could barely keep the RH in the tent down to 55% with all that. I tried adding about 40 lbs of rock salt in there too (which seemed to do nothing). I wrapped the entire 15x11 basement room in plastic and tape hoping to stop any extra humidity from entering.

My last idea was maybe totally lollipop them, removing most leaves—but decided not to risk it since I am a noob.

I have decided that it just makes no sense to try and flower in that room if I have less humid space available.



Do you have other areas that are less humid you can set up a flower area in?

Could you get an old ) or new ) fridge or freezer and dehumidify that? They seal pretty well.
I was thinking the other day about how drying in a working fridge would be nice if you could dehumidify it and have the temp a bit higher. Should be doable.

DoobieDoobs said:

Hey guys, I hope this finds you well.

Hey guys, um these past few weeks there has been constant rain where I live. I have a cheap hygrometer and well seems like when it rains humidity inside my tent reaches around 68%, and my hygrometer has a 5% error so it is (63% , 73%). which is a too much for flower I presume.

Do you guys know a homemade remedy for high humidity? Im not sure I can afford a dehumidifier at this moment, next grow for sure tho.
Thank you!

Click to expand...

Just curious where do you live?

65% humidity isn't actually that high. I've ran around that level most of the time. Sometimes I got some small rot issues but that (fingers crossed) has been corrected with extra under canopy air flow.

I let the humidty do it's thing ones, and it settled around 75% most of the time, didn't get a single issue that time but again that was with exra canopy and under canopy airflow. The key thing to avoid IMO is to not grow big colas. They look good but are a magnet to rot. Top many times, this creates smaller colars but more of them. You should yield more and reduce rot chance.

As I read around here last year, part of what can create rot is suppose to be the drop in humidity, high and low, say 70% down to 50% then back up. I keep meaning to get around to really checking this out by using a humidifier, rather than a dehumidifier. It's definitely easier to maintain 65-70% RH with huey than to maintain 55-60% with a de-huey. The plants natural respiration rate wants to push into the high 60's anyway. A de-huey is constantly fighting that, unless you live in a very dry climate, you evidently don't.

Scribe* said:

Hey Doobie,

I had the same problem with my last grow. I tried everything. 15x11 grow room in old basement coal scuttle, growing 4 Silver Haze in 5 gallon pots.

I ended with a 2000sq ft rated dehumidifier in the tent, three fans circulating air inside, 6”exhaust running and portable AC outside the tent. I could barely keep the RH in the tent down to 55% with all that. I tried adding about 40 lbs of rock salt in there too (which seemed to do nothing). I wrapped the entire 15x11 basement room in plastic and tape hoping to stop any extra humidity from entering.

My last idea was maybe totally lollipop them, removing most leaves—but decided not to risk it since I am a noob.

I have decided that it just makes no sense to try and flower in that room if I have less humid space available.



Do you have other areas that are less humid you can set up a flower area in?

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hey, thanks. No, my whole house these days is high on humidity. Anyway moving my whole tent is a lot of work xD, I have my plants scrogged and all. I guess I would move them if that meant I didn't have to worry about the humidity, but my hygrometer, says my house is around 60-70 everywhere I place it.

Flowki said:

65% humidity isn't actually that high. I've ran around that level most of the time. Sometimes I got some small rot issues but that (fingers crossed) has been corrected with extra under canopy air flow.

I let the humidty do it's thing ones, and it settled around 75% most of the time, didn't get a single issue that time but again that was with exra canopy and under canopy airflow. The key thing to avoid IMO is to not grow big colas. They look good but are a magnet to rot. Top many times, this creates smaller colars but more of them. You should yield more and reduce rot chance.

As I read around here last year, part of what can create rot is suppose to be the drop in humidity, high and low, say 70% down to 50% then back up. I keep meaning to get around to really checking this out by using a humidifier, rather than a dehumidifier. It's definitely easier to maintain 65-70% RH with huey than to maintain 55-60% with a de-huey. The plants natural respiration rate wants to push into the high 60's anyway. A de-huey is constantly fighting that, unless you live in a very dry climate, you evidently don't.

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Yeah I have a more dominant sativa plant growing, Im actually less concerned with that one, its the more indica dominant one that preoccupies me.

I read that with CO2 a higher humidity can be tolerated. I'm a noob, so perhaps someone can validate me on that one. I have really high Humidity, over 85 sometimes, La Nina! I have (1m x 1m tent) upper and lower fans, extraction fans, defoliated lower canopy, and being first grow (DWC) just want to hold off buying anymore equipment. Can anyone advise whether Humidity is higher or lower at the top of a room, compared to the bottom? I could put my next grow up a level..

I think the humidity would be even because running a fan in the room with the tent would also help lower it.

Depending on how your canopy is set up, if it's wall to wall you can have/create two temp/humidity zones, above will always be higher, using oscillating fans to get heat down under the canopy is how I get around it, no so much in the summer obviously.

If there's space around the plants then it should be relatively even top to bottom.

I grow and flower in 70-80% humidity with prefectly healthy plants. As long as you got good ventilation and airflow. You won't have problems. People worry about budrot etc. That occurs more if you got water from dew that isn't able to dry out, or extreme difference in temperatures from lights off to lights on causing condensation.

Heck, I even spray during lights on without a worry or single issue and my leaves are soaking wet. Why? Because I have good airflow.
People who grow outdoors experience rain, no problem.
Amazon forest and countries near the equator are humid all the time. No problem.


If you have excellent ventilation and airflow then I wouldn't even worry about it at all.

Look at all tomato hydroponic greenhouses their ideal humidity is in the 70-80% range and tomatoes get bottom end root from extreme heat and only occurs in the summer time. The stems get rot when the water doesn't dry off them.

In saying this. You should read up other high humidity experience as a lot of top growers are realising it is benefitting them.

Lool up a thread on icmag called "lies our fathers told us"

Also here is a quote from donhuanmatis/DJM. Look him up if you don't know

"earlier in the thread I said ive ran as high as 80% before all the way up to harvest and never had rot.."

Of course, everyones experience may differ! So don't blame me if your room is not optimal.

To me it's not as simple as just getting away with it, you want your plants to be thriving and they can't be at peak growth in high humidity because of transpiration issues, it's all slowed down and the plant's growth is restricted.

@goofy81 well that post really calms me down, I have 3 strong fans at the moment. I have a little 4th one maybe ill see how can I set it as well.

Star Dog said:

To me it's not as simple as just getting away with it, you want your plants to be thriving and they can't be at peak growth in high humidity because of transpiration issues, it's all slowed down and the plant's growth is restricted.

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I hear you out, and at first it was what i thought too.
But the thing is, plants thrive in humidity, and had to adapt to dry climates.

Here's a quote with referenced source linked.
". A dry environment will simply pull more transpiration out of the plant itself, drawn up through the roots. If the pressure imbalance goes on too long, and the atmosphere is too dry, plant's close off their stomata as a final protective mechanism to reduce moisture loss. "

Although it mentions dry environment and not actual numbers, but refert to VPD, if you look at this vpd chart ALSO linked in my reference, you'll find that for most of the temperatures ran by us its in the 75% to 85%.
People change humidity in thinking of combating issues, but in nature it doesn't work that way.


Source : https://www.cannabistech.com/articles/mastering-vpd-control-for-plentiful-harvests/

My plants and grow room conditions from the last 7 days! if anyone thinks i'm just all talk. 99% thriving.
I do however run 4 x 120cm ceiling fans as well as the CAN FAN qmax EC 355 with controller which is some top of the line gear.
As you can see in my weight chart, In the past i ran lower rh. but the pot weight graph was not any steeper. You'll notice the steep inclines happen during lines on, and the very steep lines happen during runoff. From my past experience my data shows me even at 50% humidity (not shown here) my plants aren't drinking anymore than they usually do.

goofy81 said:

I hear you out, and at first it was what i thought too.
But the thing is, plants thrive in humidity, and had to adapt to dry climates.

Here's a quote with referenced source linked.
". A dry environment will simply pull more transpiration out of the plant itself, drawn up through the roots. If the pressure imbalance goes on too long, and the atmosphere is too dry, plant's close off their stomata as a final protective mechanism to reduce moisture loss. "

Although it mentions dry environment and not actual numbers, but refert to VPD, if you look at this vpd chart ALSO linked in my reference, you'll find that for most of the temperatures ran by us its in the 75% to 85%.
People change humidity in thinking of combating issues, but in nature it doesn't work that way.


Source : https://www.cannabistech.com/articles/mastering-vpd-control-for-plentiful-harvests/

Understanding Vapor Pressure Deficit: The Weird Humidity Puzzle in Marijuana Growing

Vapor pressure deficit is an important humidity and temperature factor in marijuana growing.

growingmarijuanaperfectly.com

My plants and grow room conditions from the last 7 days! if anyone thinks i'm just all talk. 99% thriving.
I do however run 4 x 120cm ceiling fans as well as the CAN FAN qmax EC 355 with controller which is some top of the line gear.
As you can see in my weight chart, In the past i ran lower rh. but the pot weight graph was not any steeper. You'll notice the steep inclines happen during lines on, and the very steep lines happen during runoff. From my past experience my data shows me even at 50% humidity (not shown here) my plants aren't drinking anymore than they usually do.

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Yes I see where you're coming from, I'm not too familiar with vpd but I get the idea, if I'm not mistaken the 75/85% is for early veg once you get into high growth rates doesn't the rh drop to around 50/65%.

If the air is already loaded with moisture it can't take any from the plant was my thinking?

I made another post with more references pointing in the direction of high humidity if you're at all curious. It will also answer your question in some of the references.

"With less moisture in the air, the already overtaxed plant creates more issues. The good news is that constantly high humidity allows plants to keep their stomata open regularly because there’s no risk of losing moisture. ( Some Dutch scientists at the University of Wageningen in the Netherlands figured that out.)"

If the air is humid, the stomata actually OPENS because it knows there's no RISK of losing moisture.

Here's the link to my new thread if you're interested.

.... Just when I thought I had something figured out, you guys come in with proof and research.