Does VPD matter at night time {lights off} if not do I not set the appropriate VPD for lights off or keep it the same settings for lights on ??
Vpd is important during photosynthesis, but with that said to avoid things like powdered mildew or mold I keep my grow dialed in 24/7. If your within the tolerances of good vpd you’ll benefit more than you would not. I ran my 4x8 tent at 60% humidity all thru flower n never had a issue and it paid off in the end👊🏻 Hope that helps ya
Some what, so you’re saying I should keep the same settings for lights off as lights on and not changing the day/night cycles?
Vapor Pressure Deficit matters all the time. Making a change in your VPD is more a function of where your plant is during it’s life cycle. If you look at the charts VPD is higher during flower than veg. Let’s see if this chart will paste:
It All revolves around how and where the plant will get water. If the VPD is too high / dry the plant takes from the soil, too ow and it takes from the atmosphere. Keeping it at the right place keeps nutrients flowing in from the roots and keeps the mold and mildew away.
Hard to put in a reply but that is the basics of it.
Keep an eye at night as the temps drop and the Rh change which in turn will change the VPD.
BUT with all this stuff let your plants tell you what’s going on, they won’t lie to you!
This is the same chart that I use, my leaf temps are around -2, -3 degrees cooler then air temps. I try to keep air temps at 77-80F and humidity is at 45-48% so that gives me a VPD at 1.3-1.4. Should I keep this setting for night time temps?
I try to hit the same VPD day and night based on where my plants are. Right now I am in veg so I shoot for about 1.0.
How do your girls look? They happy, they “praying”, they’re going to tell you.
Prying all the time, luscious green but not a dark green. The new light was a little bright for them at first turned them down. I just got a wattt meter now trying to figure out how many watts I need to be a
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Yessir they look happy enough.
Here’s my girls at 25 days, just starting to flower. These were test beans from a breeder, autoflowers. Sorry for the crap picture.
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looking good at just 25 days what are you feeding them. I have using dry nutrients on this grow use liquid nutes on the last grow I or they didn’t seem to like it and had nutrient deficiency at an early stage in Veg. I decided to use dry on this grow plus I think its easier, but that’s just my opinion.
Thanks man!
Using Nectar For The Gods, Roman Regimen and all sorts of beneficial microbe stuff.
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thinking of using that brand of nutrients on my next grow, been doing a lot of readings on those and so far I like what i am reading
Super stuff, BUT, it’s a hell of a commitment. There’s like 14 bottles. You will need good Ph and TDS meters. But it does pay off in the end. It is Calcium based not salt as most of the stuff out there is.
Benes and humics are also important as is SLF-100. When you get into the NTFG and benes thing you are more working on the soil than the plant, very much to the plants benefit. It’s hard to describe but if you get the hang of it it’s worth it. It certainly taught me a lot about reading my plants.
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Yeah, I seen their line up and it is overwhelming if you don’t know what your doing so that is when you do some hard core researching. Reading your plant is beneficial to you and your plant defiantly a must have. I tell this to every one any body can plant a seed, but you have to know how to read it to know what it wants and needs… never assume that a plant needs something that it dosnt because it looks the way it is. Process of elimination
VPD matters 1/10th to 1/100th as much at night according to my research, so not really. I’d just make sure that your nighttime environment is set up so that your plants aren’t stressed and you don’t have any disease or pest issues.
Thank you for validating my answer above Pete. 
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I have plenty of air flow from bottom to top. I have 2 inkbird controllers and both are wi-fi, just trying to figure out where or say them what the humidity and temperature should be at night I can set day/night settings on both of them. I run with 76-80 / 40-47% RH. Just trying to figure what the temperature/ humidity is at lights off
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Did some research on this, to sum it up:
VPD at night isn’t nearly as important as your day VPD, it’s still an important factor to consider for vigorous plant growth and increased yields
I’ve got an update all about night time VPD here on the blog if you wanna learn more: VPD at Night