VPD - following chart and south they go!

Have2

Have2

Well-Known Member
Hey everyone!

I'm having some mars hydro led and well.. When I put 78-79F as temp. I measure leaf temp at ~ -3/-4 F from ambient temp. I should raise my humidity at 58% to get 1.

But, around 1, nothing works... As soon as I drop my humidity to 43-46%, they take off immediately.

Anyone experienced this? Trying to follow VPD guidance but shit... it only works when VPD is at 1.5. (when I just put the clones into the dwc bucket)

thanks for any input!
 
H

Hooda Thunkit

Well-Known Member
Try raising your temperature to 84 degrees. Just to see if that fixes things.

Alternatively, a couple guys on here consistently run their grows well outside optimal vpd and they get great results. Maybe dial in physical environment until your plants are happy and let them run. Doesn't really answer your question, but......
 
Have2

Have2

Well-Known Member
Hooda Thunkit said:
Try raising your temperature to 84 degrees. Just to see if that fixes things.

Alternatively, a couple guys on here consistently run their grows well outside optimal vpd and they get great results. Maybe dial in physical environment until your plants are happy and let them run. Doesn't really answer your question, but......
Click to expand...
Isn't heat a concern for hermies? They all tend to hermies these days, i'm not sure I want to add an additional stress :D

I wasn't looking for a right answer, just to see if there's a pattern. Thanks for your input!!

I'll try raising it to 84 but I'll need a heater to do so, a little bit chiller around here at this time of the year and leds aren't adding that much heat. :(

Another thing that is weird, once it's established, same temp, humidity at 59-62 and everything is fine. Really weird as usually, you need to have higher humidity at the beginning of their cycle.
 
cannabiscrusader

cannabiscrusader

Well-Known Member
I think Cheryl Crow said it best. If it makes you happy, it can't be that bad. Sounds to me like you do really well just reading your plants. Throw that chart out the window and do what makes them happy. Happy plants are productive plants. Plants that do shitty under perfect vpd environment are shitty. Woo them with your wind song of botanal bliss
 
Have2

Have2

Well-Known Member
cannabiscrusader said:
I think Cheryl Crow said it best. If it makes you happy, it can't be that bad. Sounds to me like you do really well just reading your plants. Throw that chart out the window and do what makes them happy. Happy plants are productive plants. Plants that do shitty under perfect vpd environment are shitty. Woo them with your wind song of botanal bliss
Click to expand...
Everytime I tried to follow the VPD, it went bad... So I'm wondering if light's spectrum can have a role into that. On that subject, if I put 300 ppdf with leds at, let's say 40" from the canopy, not good at all. Lowering the leds, lower the intensity to keep the 300, and now the plants are loving it.

But, I keep telling myself, the agricultural business can't be wrong on everything, that doesn't make anyse sense. Hence my post, trying to get my head on this particular topic and get as many inputs possible!

Thanks!
 
cannabiscrusader

cannabiscrusader

Well-Known Member
I run my lights around 18-20" at %75 after week 4 of flower. I only run them @ %100 during the stretch. %75 at 16" for veg too, unless it's a super stretchy strain. Then you need a light with more blue in the spectrum to minimize the stretch. Running the lights a bit lower not only saves the tops of your nugs from getting scorched, but it also extends the life of your light fixture.
 
Have2

Have2

Well-Known Member
[
cannabiscrusader said:
I run my lights around 18-20" at %75 after week 4 of flower. I only run them @ %100 during the stretch. %75 at 16" for veg too, unless it's a super stretchy strain. Then you need a light with more blue in the spectrum to minimize the stretch. Running the lights a bit lower not only saves the tops of your nugs from getting scorched, but it also extends the life of your light fixture.
Click to expand...
Do you know how much PPFD you're getting at those specifications?
 
Turpman

Turpman

Well-Known Member
Have2 said:
Hey everyone!

I'm having some mars hydro led and well.. When I put 78-79F as temp. I measure leaf temp at ~ -3/-4 F from ambient temp. I should raise my humidity at 58% to get 1.

But, around 1, nothing works... As soon as I drop my humidity to 43-46%, they take off immediately.

Anyone experienced this? Trying to follow VPD guidance but shit... it only works when VPD is at 1.5. (when I just put the clones into the dwc bucket)

thanks for any input!
Click to expand...
How’s your feed? When you raise RH they will transpire less. Less food.
Are you sure your RH is reading correct?
 
D

Delps8

Well-Known Member
Have2 said:
Hey everyone!

I'm having some mars hydro led and well.. When I put 78-79F as temp. I measure leaf temp at ~ -3/-4 F from ambient temp. I should raise my humidity at 58% to get 1.

But, around 1, nothing works... As soon as I drop my humidity to 43-46%, they take off immediately.

Anyone experienced this? Trying to follow VPD guidance but shit... it only works when VPD is at 1.5. (when I just put the clones into the dwc bucket)

thanks for any input!
Click to expand...
The optimal VPD for cannabis as seedlings is 0.8, 1.0 for veg, and 1.2-1.4 in flower. There's simply no need to argue on that point because we know that's how plants work. But VPD isn't the whole enchilada, of course.

High 70's and 58 is the cat's meow. High 70 and mid-40's means that your plants are transpiring a lot so they're bringing in a lot of water and that also means a lot of chemicals.

First, how do you know that your temps and RH are accurate? Are you using a calibrated hygrometer?

Check out this graphic. Check over each of those items in your grow environment. If they're all within normal parameters, you should be good to go.

If you need 1.5 to make things work, then something is out of whack.

Genetics? Fans? Are you soil or hydro?




Parameters of Growth.png

My current grow is shown here. VPD in range for the entire month. I use an AC Infinity Controller 69 with their T4 humidifier and the only thing I need to do is put water in the humidifier. I set it at 0.8 for seedling and 1.0 in veg. The stupid computer does the work.

1702355738398.jpeg

Post some info about your grow environment and something will pop up.
 
D

Delps8

Well-Known Member
cannabiscrusader said:
No idea, don't really care. Use the back of your hand if you suspect light damage. Every fixture is different too, so you have to find what works for your set up.
Click to expand...
The back of your hand was used with gas discharge because they generated IR that would heat the plants. LED's are a different story.
 
D

Delps8

Well-Known Member
Have2 said:
Everytime I tried to follow the VPD, it went bad... So I'm wondering if light's spectrum can have a role into that. On that subject, if I put 300 ppdf with leds at, let's say 40" from the canopy, not good at all. Lowering the leds, lower the intensity to keep the 300, and now the plants are loving it.

But, I keep telling myself, the agricultural business can't be wrong on everything, that doesn't make anyse sense. Hence my post, trying to get my head on this particular topic and get as many inputs possible!

Thanks!
Click to expand...
If your PPFD is 300µmol, that's mid-range for seedlings. It won't kill cannabis but you won't get much of a crop because that's about ⅓ of the light level where cannabis thrives.
 
B

Breezet23

New Member
Have2 said:
Hey everyone!

I'm having some mars hydro led and well.. When I put 78-79F as temp. I measure leaf temp at ~ -3/-4 F from ambient temp. I should raise my humidity at 58% to get 1.

But, around 1, nothing works... As soon as I drop my humidity to 43-46%, they take off immediately.

Anyone experienced this? Trying to follow VPD guidance but shit... it only works when VPD is at 1.5. (when I just put the clones into the dwc bucket)

thanks for any input!
Click to expand...
I'm Running VPS Totally in this Run. I'm trying it in Coco but I am trying VPS for the first time. I have been using Flavuh and it's Unbelievable. But I'm not sure about using VPS for Autos in Coco-coir. I'm starting my Hydro up and I'm going to try the VPS in that run. These Nutes are the Real Deal.
 
Have2

Have2

Well-Known Member
[
cannabiscrusader said:
I run my lights around 18-20" at %75 after week 4 of flower. I only run them @ %100 during the stretch. %75 at 16" for veg too, unless it's a super stretchy strain. Then you need a light with more blue in the spectrum to minimize the stretch. Running the lights a bit lower not only saves the tops of your nugs from getting scorched, but it also extends the life of your light fixture.
Click to expand...
Do you know how much PPFD you're getting at those specifications?
cannabiscrusader said:
No idea, don't really care. Use the back of your hand if you suspect light damage. Every fixture is different too, so you have to find what works for your set up.
Click to expand...
As a previous member said, can't use that when growing with leds...
 
Have2

Have2

Well-Known Member
Delps8 said:
If your PPFD is 300µmol, that's mid-range for seedlings. It won't kill cannabis but you won't get much of a crop because that's about ⅓ of the light level where cannabis thrives.
Click to expand...
As for 300 ppfd, I run this for veg (mothers) I don't need to get 500-600 ppfd.. they grow really well at that intensity.
 
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