VPD in veg vs. bloom

  • Well, we're still working on things and I imagine we'll see some bugs, some breaking, and things that need to get fixed. We'll start on the most critical things first and work our way down. We're still installing add-on's and squaring away some licensing stuff, but feel free to browse the board and we'll update everyone on when things are added, restored, or otherwise changed.

lunarman

Auto Warrior
Mar 13, 2017
3,356
9,673
0
I have read multiple times that VPD is not as critical during flowering. Curious what peoples experiences are with that.

I run on average 70 degrees F and 50% RH which gives me a VPD of 1.25. I do this during veg because its what I can manage given my climate. I'm very happy with this during veg. Plants seem to love the cooler moister air. If I went any higher temp I'd have to run a lot of water thru a humidifier I have in the tent so I stick with this. I already go thru 6 of the 5 gallon jugs of RO water every week. I can't justify adding more H2O.

But what about flower? Should I try and maintain the same FPD? Or can I drift off it during flower? I am wondering if I can reduce my RH to like 40% and save on bottled RO water expense during flower.
 

MedCzech

Tinkering in the ManCave!
Apr 24, 2018
1,759
5,963
0
Currently Smoking
Orange Biscuit, Purple Nuggets, Sour Livers, Gorilla Glue, Chem Stomper and so much more!
40 % is pushing it a bit low. 45 would be ok at that temp. Anything less than that would really add too much stress to the trichime production and that last push in weeks 5 to 8 of flower they need enough moisture to still grow and put in some mass.
Just lay some wet towels down on the floor of the grow space and you will see some gains in your RH numbers. No investment needed:)

Good luck and good growing!
 

pop22

Frankensteins Lab Leader
Gladiator Level 2
Dec 15, 2013
15,944
50,183
20
Considering the expense of RO/Distilled water, you can get an RO filter for as little as $50. I paid $79 for the one I use now and can easily make 30-40 gallons a day! I saved some ice tea plastic jugs, enough to store ten gallons of water

I have read multiple times that VPD is not as critical during flowering. Curious what peoples experiences are with that.

I run on average 70 degrees F and 50% RH which gives me a VPD of 1.25. I do this during veg because its what I can manage given my climate. I'm very happy with this during veg. Plants seem to love the cooler moister air. If I went any higher temp I'd have to run a lot of water thru a humidifier I have in the tent so I stick with this. I already go thru 6 of the 5 gallon jugs of RO water every week. I can't justify adding more H2O.

But what about flower? Should I try and maintain the same FPD? Or can I drift off it during flower? I am wondering if I can reduce my RH to like 40% and save on bottled RO water expense during flower.
 

lunarman

Auto Warrior
Mar 13, 2017
3,356
9,673
0
Considering the expense of RO/Distilled water, you can get an RO filter for as little as $50. I paid $79 for the one I use now and can easily make 30-40 gallons a day! I saved some ice tea plastic jugs, enough to store ten gallons of water
I should look in to that.
 
  • Like
Reactions: pop22

okPeet

Auto Warrior
AFN Authorized Vendor
Nov 28, 2017
130
357
0
Currently Smoking
NL#5

lunarman

Auto Warrior
Mar 13, 2017
3,356
9,673
0
Considering the expense of RO/Distilled water, you can get an RO filter for as little as $50. I paid $79 for the one I use now and can easily make 30-40 gallons a day! I saved some ice tea plastic jugs, enough to store ten gallons of water
I did get the RO Buddie. Cost me more like $100 Cnd for the 4 stage one. But what a great investment. Paid for itself quickly and I don't have to drive to get bottled RO water now. Thanks for that recommendation.
 
  • Like
Reactions: pop22

lunarman

Auto Warrior
Mar 13, 2017
3,356
9,673
0
An easier way to use VPD. Subtract 5-7 F from air temp to get leaf temp, and stay in the green.
I use an infrared thermometer to check leaf temp, but it is pretty much always 5-7F lower. I've made a few improvements in my growing lately so its hard to pinpoint what improvements came from what change, but after two grows of following VPD I'm sold on it. I put good use to a humidifier in veg and a dehumidifier in flower in order to do it right.
 
  • Like
Reactions: pop22

pop22

Frankensteins Lab Leader
Gladiator Level 2
Dec 15, 2013
15,944
50,183
20
I was hauling 20 gallons of commercially filtered water a week and said screw that lol!

I did get the RO Buddie. Cost me more like $100 Cnd for the 4 stage one. But what a great investment. Paid for itself quickly and I don't have to drive to get bottled RO water now. Thanks for that recommendation.
 
  • Like
Reactions: lunarman