VPD and "outdoor" grow problems

fordtough68 · Apr 23, 2025

New fellow here. So, I have a particular conundrum. My wife will not let me grow indoors, (bummer,I know) so I purchased a hoop house (15'x7'x7') to stay within local laws and be able to grow. Now, with that said, this is my first real grow and im trying to set myself up for success and have spared no expense. I have the spider farmer bottom watering system to make sure the soil stays nice and moist, using the coots soil recipes. I have the ac infinity 6 inch inline fan with the new ai+ controller. I have a couple of ac infinity Oscillating fans, and I have the ac infinity t7 Humidifier, all controlled by the ai+ controller. Now for the issue.

Temps......

Its getting up close to 100 degrees in there with a shade cloth on it. With the Humidifier I should be able to keep vdp within range during veg, but this means keeping humidity during the day at around 75-80%rh. I can open the windows and get temps down considerably, but then humidity drops way too low and screws vdp even worse.

Since I can only do so much with temps, can I use humidity to keep vdp within range and still be successful? During flowering I will need less humidity and will cross that bridge when I get there, but will I be ok during veg at 95 degrees with crazy high humidity?

orggrwr · Apr 23, 2025

Don't worry about VPD outdoors. Your stuck with whatever mother nature gives you. Outdoor growing is very different from indoors. It's all about providing as much air circulation as you can and then dealing with problems as they show up( bugs, WPM, bud rot, etc). I grow in a poly tunnel in summer and it's a challenge but I love it. Start a grow thread and there's lots of good people here to help you along. Good Luck

fordtough68 · Apr 23, 2025

orggrwr said:
Don't worry about VPD outdoors. Your stuck with whatever mother nature gives you. Outdoor growing is very different from indoors. It's all about providing as much air circulation as you can and then dealing with problems as they show up( bugs, WPM, bud rot, etc). I grow in a poly tunnel in summer and it's a challenge but I love it. Start a grow thread and there's lots of good people here to help you along. Good Luck

Thank you very much. I assumed this would be the case, but would like to try to keep it as close to range as I can. The w00 plus days are freaking me out. Im about to pop seeds this weekend and am trying to dial it in as best as I can before then!

Oldchucky · Apr 23, 2025

fordtough68 said:
Thank you very much. I assumed this would be the case, but would like to try to keep it as close to range as I can. The w00 plus days are freaking me out. Im about to pop seeds this weekend and am trying to dial it in as best as I can before then!

What part of the country do you live in? Climate wise?

Glomus · Apr 24, 2025

fordtough68 said:
New fellow here. So, I have a particular conundrum. My wife will not let me grow indoors, (bummer,I know) so I purchased a hoop house (15'x7'x7') to stay within local laws and be able to grow. Now, with that said, this is my first real grow and im trying to set myself up for success and have spared no expense. I have the spider farmer bottom watering system to make sure the soil stays nice and moist, using the coots soil recipes. I have the ac infinity 6 inch inline fan with the new ai+ controller. I have a couple of ac infinity Oscillating fans, and I have the ac infinity t7 Humidifier, all controlled by the ai+ controller. Now for the issue.

Temps......

Its getting up close to 100 degrees in there with a shade cloth on it. With the Humidifier I should be able to keep vdp within range during veg, but this means keeping humidity during the day at around 75-80%rh. I can open the windows and get temps down considerably, but then humidity drops way too low and screws vdp even worse.

Since I can only do so much with temps, can I use humidity to keep vdp within range and still be successful? During flowering I will need less humidity and will cross that bridge when I get there, but will I be ok during veg at 95 degrees with crazy high humidity

You really just need a tarp above with a light screen and or shade cloth. I think you would be better off controlling humidity with misters and erring on the dry side. Humidity is important even growing outdoors. As long as your flowers aren't getting cooked you should have the best of both worlds.

fordtough68 · Apr 24, 2025

Oldchucky said:
What part of the country do you live in? Climate wise?

Im in Southern Ohio, so it gets mighty hot here in the summer.

fordtough68 · Apr 24, 2025

Glomus said:
You really just need a tarp above with a light screen and or shade cloth. I think you would be better off controlling humidity with misters and erring on the dry side. Humidity is important even growing outdoors. As long as your flowers aren't getting cooked you should have the best of both worlds.

These temps are with a shade cloth on it already. As I posted this thread, I was thinking about putting up one of those small canopys above it during the hottest part of the day to see if it helps at all. Im afraid that with all of this shade and covering, im ruining my chances at a good harvest and defeating the purpose.

Glomus · Apr 24, 2025

fordtough68 said:
These temps are with a shade cloth on it already. As I posted this thread, I was thinking about putting up one of those small canopys above it during the hottest part of the day to see if it helps at all. Im afraid that with all of this shade and covering, im ruining my chances at a good harvest and defeating the purpose.

I was suggesting keeping the green house open and try to manage the humidity with misters and such. I will sometimes spray down my plants in the heat of the day if its a particularly hot day. Its just when flower time comes around you have to try to protect the flowers from too much heat and sun, the heat and sunlight can degrade the trichs and terpes. Honestly even outdoors in that environment plants can adapt to all kinds of stress and conditions.
I appreciate what you going for.

fordtough68 · Apr 24, 2025

Glomus said:
I was suggesting keeping the green house open and try to manage the humidity with misters and such. I will sometimes spray down my plants in the heat of the day if its a particularly hot day. Its just when flower time comes around you have to try to protect the flowers from too much heat and sun, the heat and sunlight can degrade the trichs and terpes. Honestly even outdoors in that environment plants can adapt to all kinds of stress and conditions.
I appreciate what you going for.

Aah, I gotcha. Unfortunately I'm going to be growing autos, so these little ladies will be in full flower during the peak of the heat im afraid.

In reality, I know my problem. Its this dang hoop house. Id width the walls in a second if our laws didn't say it had to be grown in a greenhouse. Im going to look into some misting methods, but im not sure what to do during flowering.

Glomus · Apr 24, 2025

fordtough68 said:
These temps are with a shade cloth on it already. As I posted this thread, I was thinking about putting up one of those small canopys above it during the hottest part of the day to see if it helps at all. Im afraid that with all of this shade and covering, im ruining my chances at a good harvest and defeating the purpose.

You could try an AC unit lol. but at that point you might as well be growing indoors lol

Glomus · Apr 24, 2025

fordtough68 said:
Aah, I gotcha. Unfortunately I'm going to be growing autos, so these little ladies will be in full flower during the peak of the heat im afraid.

In reality, I know my problem. Its this dang hoop house. Id width the walls in a second if our laws didn't say it had to be grown in a greenhouse. Im going to look into some misting methods, but im not sure what to do during flowering.

If its that dry where you are I wouldn't worry much about mold unless you have bugs, misting could work

fordtough68 · Apr 24, 2025

Glomus said:
You could try an AC unit lol. but at that oint you might as well be growing indoors lol

Haha, honestly that was the only next logical conclusion for me! I can automate it, so it would be pretty easy to do, just more expense. If my wife would allow it, id set up a spare bedroom as a grow room. Ironically, its just us as all the kids have moved on, and we live in a 4 bedroom house, so this would be such an easy transition!

Glomus · Apr 24, 2025

There are also these breathable greenhouse walls made of a black fabric. I believe they are designed for light dep greenhouses

fordtough68 · Apr 24, 2025

Glomus said:
There are also these breathable greenhouse walls made of a black fabric. I believe they are designed for light dep greenhouses

Hmmm, I didn't think about this. The only issue is could think of here would be the lack of humidity which I suppose could be overcome with a misting setup?

fordtough68 · Apr 24, 2025

Glomus said:
I was suggesting keeping the green house open and try to manage the humidity with misters and such. I will sometimes spray down my plants in the heat of the day if its a particularly hot day. Its just when flower time comes around you have to try to protect the flowers from too much heat and sun, the heat and sunlight can degrade the trichs and terpes. Honestly even outdoors in that environment plants can adapt to all kinds of stress and conditions.
I appreciate what you going for.

Well, I checked around and I found something that may work well with my current setup. I ordered a misters that I can zip tie to the ceiling of the hoop house, and also a timer that I can set schedules with and monitor from my phone. With my controller I can monitor temps wherever I am, and can flip it on and off straight from my phone (or just schedule it on in the hottest part of the day). It'll be here tomorrow for setup, so hopefully I'll see how it works by the weekend.

Glomus · Apr 24, 2025

fordtough68 said:
Well, I checked around and I found something that may work well with my current setup. I ordered a misters that I can zip tie to the ceiling of the hoop house, and also a timer that I can set schedules with and monitor from my phone. With my controller I can monitor temps wherever I am, and can flip it on and off straight from my phone (or just schedule it on in the hottest part of the day). It'll be here tomorrow for setup, so hopefully I'll see how it works by the weekend.

That's rad, I still think you should use a small AC unit too lol

fordtough68 · Apr 24, 2025

Glomus said:
That's rad, I still think you should use a small AC unit too lol

In all seriousness, im looking into this too. I think it would be a better solution tbh. Im trying to find an old used one that isnt digital that has a manual on/off switch that I can turn on/off with my controller app via seat plug.

If I were retired, I wouldn't mess with all the things I am, but im never home so im trying to automate everything feasible, with check ins before and after work.

orggrwr · Apr 24, 2025

I would not mist the plants. That's asking for WPM and bud rot. The main benefits of the greenhouse is wind and rain protection. I've had better luck just opening all doors and windows with several circulation fans to keep air moving. Heat is just something you have to deal with outdoors. You can research heat tolerate strains and I've read several places that kelp supplements help with heat tolerance. It seems to have helped my outdoor grows in the past several years.

fordtough68 · Apr 24, 2025

orggrwr said:
I would not mist the plants. That's asking for WPM and bud rot. The main benefits of the greenhouse is wind and rain protection. I've had better luck just opening all doors and windows with several circulation fans to keep air moving. Heat is just something you have to deal with outdoors. You can research heat tolerate strains and I've read several places that kelp supplements help with heat tolerance. It seems to have helped my outdoor grows in the past several years.

I am a little worried about the root system, but I wouldn't use misting during the flowering stage at all. But yeah, I think youre right about the temps being just something to have to work with. Im using autos and have all of my seeds already, and 90% are from atlas seeds which really prioritize outdoor strains.

fordtough68 · Apr 24, 2025

orggrwr said:
I would not mist the plants. That's asking for WPM and bud rot. The main benefits of the greenhouse is wind and rain protection. I've had better luck just opening all doors and windows with several circulation fans to keep air moving. Heat is just something you have to deal with outdoors. You can research heat tolerate strains and I've read several places that kelp supplements help with heat tolerance. It seems to have helped my outdoor grows in the past several years.

For reference, here is the temps this very moment. 106 inside, but the door is closed down and several windows are open, with the 6" exhaust fan going at 100% and both Oscillating fans at 100%. It would be closer to outdoor temps with the door open, but then I think I run afoul with the laws if its not closed up. Also, I don't have the Humidifier or dehumidifier set up yet. Planning on doing that this weekend.

VPD and "outdoor" grow problems

VPD and "outdoor" grow problems

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