Hey guys. Back with another question. We know that VPD needs the leaf surface temperature to be fully accurate. In my time as a new grower, I've been trying to achieve perfect VPD, but I have run into an issue. Of the two mature plants in my tent(there were 3 but one was ready for chop), they all have different leaf surface temperatures. This makes sense to me as they are different phenos and not great genetics(growers choice). My question is, how can I achieve a good VPD? CAN I maintain a good VPD? I think I'm seeing now the answer is no, but then would it at least be beneficial to follow a basic VPD chart not specific to leaf temp? 3 different strains three different leaf temps.
VPD useless for multiple plants in same environment?
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I would just shoot to keep all the plants more or less within the good range. You don't need to hit one perfect number, anywhere nearby is likely as good or better than what many growers can manage.
Good luck with it.
I would just shoot to keep all the plants more or less within the good range. You don't need to hit one perfect number, anywhere nearby is likely as good or better than what many growers can manage.
Good luck with it.
Thank you. I had assumed as much but wanted advice from someone more experienced. It was driving me mad trying to figure out how to get each plant in the VPD range they would need according to leaf surface temperature.
I just try to keep the tent as close to 80*/60% as I can and it seems to work pretty well for my ladies.
Nice that seems similar to what I'll try to do from now on. Do you try to keep those numbers the whole way throughout the grow?
Yep, I run perpetual so I aim for numbers that will keep everyone happy.
Wow thank you so much. I actually am doing perpetual as well so this seems like a great solution. Thank you so much for your time!
No worries! I've found that controlling the temp in the lung room is way way way easier than relying on fans. Keeping my room at 69-71 degrees means I can run the fan pretty low and keep the tent at 80. The humidity in my room stays around 45%, so keeping the rh between 50 and 60 happens pretty naturally just with watering the plants. I do have 60 gallons of soil in my 4x4 though, so that helps keep things stable as well. The most high tech thing in my tent is my oscillating tower fan that has an "auto" mode where it will increase speed depending on when you turn it up. Not a precision instrument by any measure lol but I turned it up to 2 at 80* so if it goes over 79* it will bump up from 1 to 2 and then on up to 6 as needed. Max I've hit since I adjusted things was 83ish but my humidity was over 60% so I didn't stress over it.
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Take multiple readings from different leaf surfaces and create an average. That gives your offset temperature to calculate into your actual VPD. The difference from seed to harvest in humidity is a 15% difference so as long as you remain consistent you aren't going to see retarded growth.
They are all reading different temperatures probably because they are different heights and or there are hotspots in your space, not due to different cultivars. What temp and and humidity do you consistently run?
Honestly the big thing is I haven't had a consistent temp and humidity. In 10 days, I will have been growing for I believe 5 months exactly to the day. I'm very new and it started out a bit rough. I tried germinating 5 seeds and all of them except one germinated. I put them in the coco and only two ever popped up. I was running these two without following VPD the first couple weeks. Then I read something about it. Well roughly one month after that, after practicing how to germinate seeds, I tried again with a 3 pack of cream caramel autos. I ended up germinating all 3, and by my error I killed two of them. So this left me with two plants entering flower, and one seedling. At this time, I maintained a VPD between 1.2-1.6, however I was noticing it seemed like my seedling was having a hard time growing. I erred on the side of caution though and decided not to risk moldy buds. Recently I haven't had a set temp and humidity, because I've been seeing what works best for each plant. I think I more than likely don't have any hotspots, mostly because I have so much air circulation in the tent. I have an inline fan bringing in fresh air, two small fans that push air around the outside edges of the tent, one fan that pushes air around the canopy and one fan pushing air underneath the canopy. This is in a 3x3. The different heights thing is definitely plausible. Though I will say the biggest difference I have between plants is 6 inches so the height difference isn't huge.
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