Try and make this as short as possible.
Turned 50 this year and been growing herb for 15+ years (veggies for 35+). Herb growing all under 2 600W HPS lights for flower and in October I invested in 2Growcraft X600W LEDs. I never looked at VPD under my HPS style but now that’s all I here for LED. So far a few months in I have not changed much, I wanted to see what the difference was and besides bleaching a few buds until I raised the lights all the way up in my 4X8 tent.
Ignoring VPD, my leaf temperatures range between 80 and 82 degrees Fahrenheit, and my RH fluctuates between 20 and 55%.I am not using any A/C, Humidifier De-Humidifiers. MY VPD is always off the chart when looking at my ACInfinty 69 Monitor. However, my plants are praying and look as good or better than they did with HPS.
If I invest to into this VPD range, will it really benefit me that much? If you look at my IG you will see my plants don’t have much more room for resin production. If its yield increase by 10% or less I don’t see the benefits versus the negatives.
I’ve been around along time and there is much misinformation about this plant and how to grow it, watering, genetics, terps, concentrates….OK OK entirely different subjects all together. Back on track, I still am open minded but thinking this is what I call Market-Eering. When Marketing goes to an Engineer and says how can we make more money? I know this from my 30+ years in the Consumer Electronics Industry and 17 years working for a CE manufacturer in Engineering 😊.
Grow the same cultivar indoors and under the sun a few times.. there is just something about that sun. Plants that outside under the sun photosynthesis and exhibit expressions you just cannot reproduce indoors and VPD is all over
So DGC what’s your input?
I look at VPD as more of a guideline instead of a hard rule.
The real effects of being too far out of range mainly revolve around transpiration and root uptake. If you’re too low, it can cause rapid uptake from the root zone and this can cause some nutrient overload. It also stresses the plants.
If it is too high, your plant won’t transpire as much, meaning it wont drink as much, which can create wetter soil conditions around the roots. This can become anaerobic, it can alter the pH and that can alter nutrient availability and ultimately lead to lock out of certain nutrients, not to mention other potential root issues…
So, do I bend over backwards to get it exact… no, but I do make sure I’m in the general ball park.
Dude, if it ain’t broke and you like the smoke……. if your restless and want to push your talents…. this is a totally up to you thang. It can be hard to keep up with all the new equipment. You do what makes you smile.
Thank you , I think we will just keep things as is for now.
VPD is an advanced metric and it’s not good or bad, it’s just a measurement involving the air temp, leaf temp, and RH. It is entirely up to you if you find a vpd measurement is useful or not.
I don’t know what misinformation you may have read, but I can clear it up.
Plants in a high VPD environment will not show symptoms until you introduce nutrients. The plants can drink water all day.
High VPD means there is a large difference between the vapor saturation of the leaf and the air vapor pressure in the room which results in rapid uptake of water and nutrients due to high transpiration rates. Grow lights, especially HID, and air movement can exacerbate the drying effect of the high VPD.
The result of high VPD with a nutrient solution that is too concentrated will cause the plant uptake too much; this will greatly effect immobile nutrients and probably lead to a lockout from too much calcium uptake.
In this type of environment, a lower concentration of nutrient solution is advised to still grow healthy plants. Though, reduction in photosynthesis in inherent.
VPD becomes much more critical in a high co2 environment because stomatal opening is key to gas exchange. Generally, dialing in VPD will make any indoor grow more efficient, but there is no sense in raising co2 levels if plants aren’t opening their stomata enough to use it all.
In a tent, however, trying to dial in VPD by elevating the RH to tropical levels can do more harm than good depending on your geographical location and time of year. Most tent growers I’ve seen are using humidifiers in the tent and that just doesn’t work very well to begin with and I wouldn’t trust the VPD calculation. Tents run better with a lung room….but I digress.
All that said, I’m growing a sealed, co2 rich environment so VPD is very important to me; but I don’t calculate it. I can tell how much my plants are transpiring and I can see the effects on the leaves.
Understanding VPD is helpful, calculating it is for nerds.
*will not show symptoms of high VPD
When you talk smart like that, I have to look up from the view of your nipples. Your too pretty to be so smart.
Thanks for the input and think we will no start chasing VPD at this time.
I only desribed high vpd because that is more common, but just to be more thorough….
low VPD has mostly the opposite effect. Plants can’t transpire and the risk of molds and pathogens is greatly increased.