How to control humidity!

Hi. I’m new to growing and hydroponics itself. I’m having issues with controlling the humidity in my grow tents. I have a humidifier and a dehumidifier. I’m at 80% in my veg tent but how can you slowly lower the humidity over the weeks when I move it to flowering? Thank you so much I welcome any and all help.

80 is high. Don’t worry about slowly titrating your humidity down. Adjust the settings on your dehu today down to 45%.
If you’ve consistently been at 80% you shouldn’t wait or worry about slowly doing anything.
Get some ventilation in there as well! A circulating fan and a 4" inline exhaust should be sufficient.
What size is your tent?


Thanks so much. I just got the humidifier because ive been running 46%- 52% without and thought that was to low. Have 2 fans but no exhaust fan in the veg tent. With heat and air running to both tents 45% humidity will be much easier to keep. Do I want around the same humidity in both veg and flower? Do have exhaust fan in flowering tent along with 2 fans.
Turned the humidifier off… Glad I don’t sleep much and thanks so much for the response!!

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Technically speaking you can get away with higher humidity during earlier phases of veg. In fact I have personally found that some strains, especially sativas with thai and south American origins, seem to thrive in higher humidity in EARLY veg. But you MUST maintain your circulation and ventilation. Keeping the air moving in and out is important otherwise you’re just moving the same wet air off the walls in your tent.
Plants release oxygen due to photosynthesis so you want to make sure they’re getting a fresh supply of carbon dioxide and flushing that “stale” air out.
Now, once my girls start to bush up and are about 12-18" high I drop my humidity. You don’t want high humidity and bushy plants. You’ll get fungal infections and once that happens good luck. It suuuuuuucks.
In flower, keep it low. Super moist buds have the potential to rot. Yuck!
So long story short:
Early veg (like from sprout through week 3 or 4 depending on the bushiness): they can handle around 70%.
Mid veg CAN deal with 60% but they don’t thrive so 49%.
Late veg through flower I keep it at 45-48% ish.
Fungi begin to thrive at 50%+ and 75 degrees +.
Again, this is my experience, in my settings with my strains, but the information about the fungi is not an opinion.
However!!! If you’re set on keeping humidity higher you can sort mitigate that growth by ensuring adequate circulation AND ventilation. Make sure air can get EVERYWHERE in your plants, defoliation appropriately, spread your branches out by tying down, etc.

I hope that helps a wee bit. Shout out whenever you need to for help on anything!

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I use high humidity around 70% during veg and early flower. It’s about the time I start to see trichomes that I vent my tent differently. At first a small fan pushing air out and another pulling air in does the job. That helps keep the humidity up during this time. I defloiate my plants and set them up so they flower only where I want them to. Lollipoping. I do that before flower and don’t trim the plant again until they are ready to be chopped. Well maybe a fan leaf here and there.

Once the trichomes start showing up I hook up my exhaust fan. This is what I have.

Only problem I have with it is wishing I had gone with the 6 inch instead. Other than that the fan controls the environment pretty well. It will run the fan to keep the humidity and temps where you want it.

Once the big fam goes in I keep the humidity 50% and below. Also a fan blowing on the plants will help prevent mold and other problems from occurring

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The RH is dependent on what temp you run the tent at. There is a chart somewhere around you can use to see which rh is needed at what temp.

VPD chart. Vapor pressure deficit

There are different ones for flower and for veg.

I run mine at 85F per light recommendations and that calls for around 70%rh