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Walla Walla Wa.

It's important to turn on your exhaust fan's at night if possible to get rid of the excess humidity or you could try raising the temperature a bit. If the VPD is too high then using an evaporative cooler can help bring it down or shading or good air movement but not directly on the plants.

5/22/2025 1:59:41 PM

Eugene,OR

I wouldn’t say that I “discovered” VPD. I just learned about VPD when I was studying greenhouse growing. Maybe I’m the first giant pumpkin grower you knew who realized how important VPD is. If I discovered it I would have named it something like “Russ’ Big Secret That He Will Share With Nobody Ever.”

5/22/2025 5:43:18 PM

Vancouver, British Columbia, Canada

RBSTHWSWN - doesn’t make a good acronym - I’ll stick with VPD. It will be hard to manage VPD without a very robust greenhouse set up as one must either control for humidity or temperature to hit the right target. I have put a small dehumidifier in my set up to try to keep the high humidity down when I shut the greenhouse up at night - uses a lot less energy than a space heater which I also run at night to avoid too low nighttime temps and poor VPD. Also living in Vancouver we have a different VPD (Police Department) who will be called if I see anyone approaching my pumpkins in an aggressive manner.

5/22/2025 7:16:26 PM

Vancouver, British Columbia, Canada

Correction - RBSTHWSWNE - forgot the Ever!

5/22/2025 7:19:21 PM

Richmond, BC, Canada

Russ, you definitely are the 1st to talk about VPD that I know of ! Are you implementing VPD principles in your greenhouse?
Mike, on the otherhand has broken so many city bylaws that the VPD(Vancouver Police Department) will implement a few summons on him lol. My thanks to Mike for explaining VPD to me and now I'm implementing those priciples tonight. Water shut off to reduce humidty. Diesel heaters turned on to raise the temperature. My plant is growing so fast it will be hard to notice a difference. Stay tuned.

5/22/2025 10:34:11 PM

Eugene,OR

I use it as a target. My ideal is 1.2, but I feel like anything between 1-2 is good. I do not have a dehumidifier, so I will never be anywhere near perfect. It is kind of like living in a house without an air conditioner. You do your best to create comfortable living conditions. It is much better than just throwing your hands up in the air & giving up!

5/22/2025 11:34:04 PM

Torrance, Ca.

So in other words Dave, keep you fans on all the time!:)

5/23/2025 10:05:14 AM

Richmond, BC, Canada

Yes, I'm running 15 fans 24/7. I'll post a pic of the fans.

5/25/2025 10:12:46 AM