Question for you hydro guys/gals using LED. What temp and RH are you guys shooting for during seedling, veg, and flower? And do you have a specific VPD range you shoot for at each stage? Please feel free to throw in any other useful tidbits of info about the rate in which you drop humidity levels etc.
What's the optimal temp and RH ranges when using LED
- Thread starter 420Mn
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Billy the Mountain
Well-Known Member
VPD influences transpiration rates; i.e. how difficult it is for the plant to move water through the leaf.
Lower VPD for seedlings, and veg; higher VPD for flowering is the general rule of thumb.
A decent summary of VPD:
Lower VPD for seedlings, and veg; higher VPD for flowering is the general rule of thumb.
A decent summary of VPD:
Understanding VPD and Transpiration Rates for Cannabis Cultivation Operations
This article explores how vapor pressure differentials (VPD) affect transpiration rates in cannabis plants. Understanding of VPD at different temperatures and relative humidities, and its effect on this process, is important to gain maximum plant growth.
www.cannabissciencetech.com
Thanks for sharing that. I've dove into reading up on vpd and transportation rate. I'm guess I'm more curious about what vpd and temp ranges to shoot for at each stage of growth as vpd can be reached at many different temps if the humidity level is in range.VPD influences transpiration rates; i.e. how difficult it is for the plant to move water through the leaf.
Lower VPD for seedlings, and veg; higher VPD for flowering is the general rule of thumb.
A decent summary of VPD:
Understanding VPD and Transpiration Rates for Cannabis Cultivation Operations
This article explores how vapor pressure differentials (VPD) affect transpiration rates in cannabis plants. Understanding of VPD at different temperatures and relative humidities, and its effect on this process, is important to gain maximum plant growth.www.cannabissciencetech.com
Mont@n@
Well-Known Member
Hi, I keep my flower room at 80-82f (A/C) since my room with 18 plants runs at 60-73% rh mid flower up to harvest.
I use this VPD chart and never fails unless human error fuck things up lol
happy growing
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Grow Monster
Well-Known Member
That's super high humidity for late flower. At that temp u should be more in the 45% range. If I ran mine that high I would got mold or bud rot for sure. Especially dealing with sativa's going 12-14 weeks. This is the chart i like to use. its a bit different then yours but if it works for u and your environment cool.
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Thanks for taking the time to share your flowering method.
Mr. Mohaskey
Well-Known Member
Personally I use 82-84 degrees throughout. Humidity at 70% seedling, 60-65% veg, 55% early to mid flower, then 50% late flower.
Now that's the info I was searching for! Thanks you!
rkymtnman
Well-Known Member
if you run high RH, make sure you have good air movement indoors
Thanks for that heads up! What's considered high humidity? And yes, I have decent air movement. I think lol
rkymtnman
Well-Known Member
for veg, i think 60 to 70% is good range. for bloom, 40 to 50% is good.
I'm not sure how to determine when a plant is considered to be late in the seedling stage or has entered the veg stage. Running a Google search just basically says "when the plant has developed a large number of fan leaves". A noob like me has no clue what is considered a large number of fan leaves, lol. I've been keeping RH between 60-70% throughout the grow, shooting for 65-70% in the beginning. Good to know I'm currently within range. Thanks for the advice, man!
Modern Selections
Well-Known Member
That VPD garbage is a main reason for the flood of lower quality cannabis. 80 degrees and 70% humidity in flower will not yield high quality cannabis.
VPD is great for commercial greenhouses with Ag crops, etc
If you are growing in a room indoors the best temp/RH to strive for is Veg 77-80/50% Flower 72-75/35-40%
Cuttings or germination 88/high humidity
VPD is great for commercial greenhouses with Ag crops, etc
If you are growing in a room indoors the best temp/RH to strive for is Veg 77-80/50% Flower 72-75/35-40%
Cuttings or germination 88/high humidity
Kerowacked
Well-Known Member
Part of the problem with vpd is knowing leaf temp which is usually higher than air temp. I don’t do hydro but notice more foxtails above 80°F.
Billy the Mountain
Well-Known Member
I'm afraid you have it backwards.
The leaf surface temp will always be lower than the ambient air due to transpiration, usually ~3-5 degrees.
Same principle by which sweating cools the skin surface temp.
VPD doesnt have a damn thing to do with flood of lower quality cannabis. Selecting for terps instead of the effect, and tons of people growing that don't have a clue what they are doing is the reasons for lower quality. Keeping VPD in range as best as you can is all you can do, depending on your climate it will be easier in certain times of the year than others.
Kerowacked
Well-Known Member
You need an infrared thermometer. My leaf temps are always slightly higher under led’s, always.
Billy the Mountain
Well-Known Member
I do have an infrared thermometer and the readings are always a few degrees less than ambient, as expected.
It's likely that your thermometers are not in sync with one another. Try using your infrared thermometer on something
with a similar emmisivity to a leaf, ~.95, (wood and water are very close) that's acclimated to the tent's temp.
Compare that readings
Kerowacked
Well-Known Member
You are raising an interesting point Billy. Most articles indicate that leaf temps are higher than ambient, like mine, but logic tells you the leaves are working more efficiently when the leaf temp is lower. Almost of primary importance when deciphering vpd. Food for thought.
Mr. Mohaskey
Well-Known Member
I never paid attention to VPD until I switched to LED lights from HPS. Then it made sense once I started digging into the numbers and the logic.
Commercial garbage has nothing to do with VPD. Rather it is all about cutting too early before it's ready just to please the bean counters, and rushing the cure.
Commercial garbage has nothing to do with VPD. Rather it is all about cutting too early before it's ready just to please the bean counters, and rushing the cure.