VPD and plants response.

[keep it real.]

Can we also take a look at how far technology has came with these lights…. Back when I was growing no one in their minds would flower under leds. Now you can keep them 30 inches away and still have adequate lighting.. only thing led was good for was veg, mothers and popcorn buds..

 

[PadawanWarrior]

I would never haha! He was talking about his VPD of 3.3. That’s a lot of water uptake, and anything else in that water.

 

[calvin.m16]

Can we also take a look at how far technology has came with these lights…. Back when I was growing no one in their minds would flower under leds. Now you can keep them 30 inches away and still have adequate lighting.. only thing led was good for was veg, mothers and popcorn buds..

LED has come a long way, I use T5 in Clone, LED in VEG and HPS in BLOOM. I have ran LED in bloom it isn't as good for me. I would like to try some of these new flowering spectrum LEDs though and see if they can produce some hammerheads. If it ain't broke don't fix it in my opinion.

 

[James Bond23]

less is more do not run 3 EC like these shitty nutrient lines recommend. If you need 3 EC of strength their nutrients suck dick. I feed plants that are 5-6 ft tall 2.0-2.2 EC with 1200 PPM Co2 and 1.6 to 1.8 VPD with 1000w Double Ended HPS and get 21 oz a plant. more EC will just cause problems and if you get a deficiency at 2+ EC throw the nutrients in the nearest trash bin and find something else.

Agree 3 ec is just a joke your just throwing money down the drain 2 2.5ec max if the strain is good for it I also use de 1000watt hps and co2 how high do u hang the lights above plant canopy

 

[Wastei]

Has anyone else tried to dial in their leaf VPD and notice their plants just won’t allow it?
over the past couple days I’ve noticed the more I inch my humidity down the lower the leaf temperature becomes. I understand why this occurs, but it also pushes me further away from proper levels.
Plants are healthy and I’m not going to ruin a grow chasing a number but I would like to know if other people have had similar scenarios?
Tent is currently setting at 82F with 58% humidity under LEDs with a 68.1F leaf temperature, the medium temp is 72.1.
Iv noticed the warmer temps appear to be favorable to this grow but not the lower humidity, seems to have the healthiest looking leaves when at 70% or just above.
This is my first grow after 8-9 years.

How do you actually measure leaf temps? This is the most common misconceptions that you can use cheap IR thermometers without proper calibration for the intended purpose. I've had those being anything from 5-10 degrees celsius off from the actual.

VPD is a recommended range but it won't tell you what the optimal is, only the plant itself can tell you that.

Like others suggested less is more when it comes to cannabis and nutrition. Don't follow manufacturers recommendations, follow recommendations found on this site from people's own real experiences and results. Manufacturers only want your money and interest from posting high numbers for marketing purposes.

 

[coreywebster]

How do you actually measure leaf temps? This is the most common misconceptions that you can use cheap IR thermometers without proper calibration for the intended purpose. I've had those being anything from 5-10 degrees celsius off from the actual.

VPD is a recommended range but it won't tell you what the optimal is, only the plant itself can tell you that.

Like others suggested less is more when it comes to cannabis and nutrition. Don't follow manufacturers recommendations, follow recommendations found on this site from people's own real experiences and results. Manufacturers only want your money and interest from posting high numbers for marketing purposes.

Also how's air temp getting measured..
Would seem between two inaccurate measurements it would be easier to have such a huge difference

 

[1212ham]

How do you actually measure leaf temps? This is the most common misconceptions that you can use cheap IR thermometers without proper calibration for the intended purpose. I've had those being anything from 5-10 degrees celsius off from the actual.

VPD is a recommended range but it won't tell you what the optimal is, only the plant itself can tell you that.

Like others suggested less is more when it comes to cannabis and nutrition. Don't follow manufacturers recommendations, follow recommendations found on this site from people's own real experiences and results. Manufacturers only want your money and interest from posting high numbers for marketing purposes.

How do you calibrate an IR thermometer for measuring leaf temp?

 

[Billy the Mountain]

The easiest way to accurately determine a leaf temp offset is to measure a healthy transpiring leaf and a non-transpiring leaf in the same environment with the same IR gun.

The only variable is the leaf's transpiration, the inaccuracy or offset of the IR gun remains constant.

There are other ways to adjust the emissivity and offset of the IR gun for more general use, but the above method is very accurate for the task at hand.

 

[Delps8]

How do you calibrate an IR thermometer for measuring leaf temp?

Check YouTube. Briefly, change emissivity on the thermo to that of water and then do a 2 point calibration using an ice bath and then boiling water, with temp for the latter corrected to altitude.

Re. VPD - the phrase "chasing" is pejorative and I've noticed that many growers who use that term seem not to be that familiar with VPD.

There are optimal values for VPD but what does optimal mean? To my way of thinking, it means transpiration rates will be such that you don't have to change your normal watering practices and that you can run standard strength nutrients.

VPD is nothing more than one number to describe a range of temperature and RH values and VPD is not restrictive-it's simply a way of telling you what the "feels like" temperature is to your plants. It's a handy way to determine if your plant is going to be transpiring a lot, if VPD is higher than optimal, and, if it's lower than optimal, that there might be transpiration and mold/fungus issues. It's a measurement that a grower uses to understand what's happening in the grow environment.

Unfortunately, growers have glommed on to idea that VPD is an end itself. I'll admit that I labored under that perception when I started growing. It took a while to understand that it isn't the goal, rather it is just a signpost along the way. Cannabis will do fine, even under very high VPD, as long as the grower compensates for unusual conditions.

If your VPD is 2.x, for example, you're going to need to make sure that your plants get enough water and that your nutrients are diluted enough to avoid nutrient imbalance. Within reasonable limits, a VPD of X, in and of itself, won't kill a plant. I wouldn't grow a plant at VPD of 2.x but it won't kill the plant if VPD hits that value intermittently, as long as you tend to your plants.

Again, VPD is nothing more than one number to describe a range of temperature and RH combinations. Take a look at a VPD chart and you've got to have a really harsh environment to get to unusually high or low values.

As an analogy, humans rarely die by over heating but, even in moderate temperatures, we're dead in a few days without water.