VPD HELPING??

[DrOgkush]

I’m a firm believer in the sweet spot. Don’t be afraid of humidity. I run 84F ambient, 79 lst
With my humidity between 71-77%. That’s early veg. Then for most of the plants life I run closer to .7- 1.0 kpa. Then slowly adjust down every week of flower until I remove the humidifier completely. This is my second grow paying attention to such detail. And the difference it has made, was something I’d never expect. I open my tents and smile everyday with absolutely no problems anymore. I just keep my ph and ec correct along with the recommended environment. Co2 levels are naturally 6-800 because we have 5 humans, 2 dogs, 5 cats, Guinea pig and a large fish aquarium. Lung room is my bedroom so mine and my wife’s breathing plus cats. Really up the levels. And I now use dry amendments in Promix. Grow dots and dr earth. And I feed very heavy in the beginning. When my humidity gets to low. My plants will burn. Iv been growing in the high desert where humidity levels are rarely in the 20s. Usually around 18%. Ever since iv adjusted those levels. Growing seems a lot less complicated. Or I just made it less complicated for myself. Happy growing!!

 

[silk689]

sorry I am 50 days in so just finished week 7 and the strains I’m running are done at week 8-9 . Is my first indoor grow so looking to pull asap I dimmed the light back to ab 50% and have it over a ft away. It’s a SE3000 nothing crazy. I have temps down now to around 77 lst -2. It is digital but the problem is it creates super hot air I’m talking above 90* which is way too hot for how mild it dumidifies so during lights off I try and use it only when it gets over 40. But your recommending 35% or lower during lights on ? And then just do the best I can about rh during lights off ? I don’t have a problem getting lower rh during lights on I just have been using a humidifier in my lung room to help keep it around 40 .. cause keeping my tent extra dry during lights on and more humid during lights off seems backwards to me or am I off ?

Ok heres the trick. Ur going 35% humidity at ur stage because it will increase Trichome production and also prevent any possible mold occurring in ur buds. Dont concern yourself too much about lights off numbers. Just try to perfect it as much as u can when lights are on.

Do not pull ur plants too early. U should be examining your trichomes at this stage through a 60-100x microscope minimum. I suspect the trichomes are very VERY early and maybe still in its “crystal clear glass looking type stage”.

Maybe show us some pictures of the plants close up and a meter away just in case we spot anything else u that needs doing.

 

[DoubleAtotheRON]

@PadawanWarrior , Can you just put a Portocool swamp cooler in your room to get those RH levels up?

 

[CWF]

Question: does VPD matter when the lights are off? Do plants transpire when lights off? I've searched my ass off and can't find a definitive answer. I run a humidifier 24-7 to keep it in the good range, but do I really need it in the dark period? TIA

 

[DoubleAtotheRON]

Question: does VPD matter when the lights are off? Do plants transpire when lights off? I've searched my ass off and can't find a definitive answer. I run a humidifier 24-7 to keep it in the good range, but do I really need it in the dark period? TIA

Yes, they do transpire at lights out. This is why you'll see a RH spike after lights out. The duration of that? I have no idea. But, from the research I've done as well, VPD is not as important at lights out because there is no photosynthesis going on. Still important to keep your RH in check tho for other reasons.

 

[Billy the Mountain]

Yes, they do transpire at lights out. This is why you'll see a RH spike after lights out. The duration of that? I have no idea. But, from the research I've done as well, VPD is not as important at lights out because there is no photosynthesis going on. Still important to keep your RH in check tho for other reasons.

Transpiration is minimal in C3 plants in the dark period

RH spike at lights out is primarily due to the temperature drop

 

[CWF]

Gotcha. THANKS!

 

[DoubleAtotheRON]

Transpiration is minimal in C3 plants in the dark period

RH spike at lights out is primarily due to the temperature drop

Kinda why I said "the duration"...Prob a spike, because my temps don't drop that fast. I keep it within a few degrees between lights on/off. But, it does level out after a while.

 

[LeastExpectedGrower]

1 - firstly how many weeks flowering does your strain go to?

2 - try to stabilise your temp to 75%f dead on if you can. Does ur led lights allow u to turn it down a tad bit more?

3 - since you have a dehumidifier, is it a digital one? If so during lights on, program it to hit 35% dead on as ur in week 7. No higher then that.

4 - dont worry too much about ur RH when lights are off IF you can do the above i am suggesting. You said you have fans running thats moving air around which is good.

5 -pull off any fan leaves thats causing the canopy to be crowded so air circulates better.

6 - Always stop using the VPD chart AFTER week 4 of flowering. It will throw u off sync with high humidity numbers it suggests.

Eh. 75F with LEDs? Once you check your leave surface temperature, that's going to be a bit low. My measured LST is -2.5f degrees, so nailing 75f temp in the room is 72.5f to the plants. I'm consistently running in the 82-85 range with lights on, which is maintaining 79.5-82.5F. I think you'll find that lots of people are doing similarly here.

 

[PadawanWarrior]

@PadawanWarrior , Can you just put a Portocool swamp cooler in your room to get those RH levels up?

I've thought about it, but I'd have to run a line to keep it full. I'm sure I'd be filling that thing daily by hand I'm guessing. I'm just growing in my bedroom for now, to keep it legal. I'm just a small time grower.

 

[silk689]

Eh. 75F with LEDs? Once you check your leave surface temperature, that's going to be a bit low. My measured LST is -2.5f degrees, so nailing 75f temp in the room is 72.5f to the plants. I'm consistently running in the 82-85 range with lights on, which is maintaining 79.5-82.5F. I think you'll find that lots of people are doing similarly here.

your forgetting 1 little important detail buddy. He said he was in week 7. I would agree with u if he was early into flower but hes NOT. Decreasing temps & humidity in the last few weeks is something i and all my fellow gromies have done for many many years. It works great.

 

[DrOgkush]

Question: does VPD matter when the lights are off? Do plants transpire when lights off? I've searched my ass off and can't find a definitive answer. I run a humidifier 24-7 to keep it in the good range, but do I really need it in the dark period? TIA

When the plants not photosynthesising, vpd is not important. However like said above. Your humidity still needs to be in check for obvious reasons. You don’t want to have a Dew point in your tent. That’s when all that bad bacteria forms. And you also don’t wanna massive swing. So airflow is quite important during lights off. Keep your girls in the “sweet spot” during lights on and pay attention to rh during lights off. Then adjust accordingly. I keep my flowering tent humidity during off time at 35-45%. Then during on around 55-60%. That’s me. It’s hard for me to keep my flower tent in the sweet spot at all. So I aim for as close as I can get. But my veg tent stays around .6 .7 kpa pretty much at all times. And ill never do it another way now iv been learning about it this last year. Been a huge game changer in my veg tent with out a doubt.

 

[King Avitas]

your forgetting 1 little important detail buddy. He said he was in week 7. I would agree with u if he was early into flower but hes NOT. Decreasing temps & humidity in the last few weeks is something i and all my fellow gromies have done for many many years. It works great.

Yep, at a certain point it all becomes about terpene preservation. At that point VPD goes out the window in my grow.

 

[silk689]

Yep, at a certain point it all becomes about terpene preservation. At that point VPD goes out the window in my grow.

Iam with you on that one my bro 100%