Pulse VPD

LED Soil grow. Goal VPD 1.0 as said on the web site. 80 degrees with 70% Rh. RH seem really high to anyone else? Condensation on the walls of the tent. Only in week 3 from seed in VEG. Should I trust this?

4 Comments

jmystro on December 19, 2019 at 12:51 pm

Mold loves it above 60% with low light and high temps. Always keep that in mind. Even with adequate light, I never go above 65%. Things to watch for with high humidity would be clones in low light. Lower shaded parts ofr a clone are vulnerable to water molds that cause stem rot.

Coach Steve on December 19, 2019 at 7:04 pm

Yeah I had similar questions. I just got the leaf temps where I wanted then adjusted humidity up until it felt nice. Not sure if a small space/tent is going to work the same way especially when adding water to the air rather than it being a natural occurrence. My bro science, but maybe I”m in the neighborhood of science. Go off of feel and visuals. By the way, the pulse accuracy is +/- 3% RH.

KevmedHaze on December 20, 2019 at 10:18 am

Cant you bring the temps down to adjust to where you want it? Im not a expert! As a matter of fact im just getting into this(vpd) myself. My room is around 22c(72f) so im trying to bring my rh down. From 60 to 55-50rh to try to follow the chart. Im 7weeks into veg. In a tent thats in a cold area. My new light doesn’t put off much heat( sf 2000) so battling with temps, but I’ve seen good growth so not too worried thats why i suggest maybe bringing temps down? Idk following for info anyway! Stay high and good luck!

SOUP on December 20, 2019 at 2:45 pm

VPD recommendations are usually based on what will give optimal biomass growth rates, not actual best practices for growers.

70% humidity is great for growing a leafy bush in a greenhouse, but it’s not ideal for trichome production or for indoor growing. When adjusting your environment for growing indoors, VPD shouldn’t be the only thing you are considering.

Also keep in mind, VPD is dependent on both temperature and humidity, so you can play with both of those factors to get things better dialed in. Dropping your temps a bit can help you to stay in the ideal VPD range without running your humidity too high.

Maintaining ideal VPD is important, but not as important as trich production and keeping my walls from sweating. You want to try to keep your VPD as ideal as possible, but you have to balance that with not messing up the rest of your grow.

This VPD at article from Pulse talks about some of this stuff. They also recomend different VPD levels for different stages of growth. Check it out:

https://PulseGrow.com/blog/vpd

They recommend

Clones: 0.8
Veg: 1.0
Flower: 1.2 -1.5

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