VPD: The Final Stages Of Life

[OG-GeMann]

Lets talk about VPD in flower, Am I supposed to follow VPD when in flower. (the final 2 weeks) humidity 30-40% temps 70-75F will give me a VPD of 1.5-1.65 {leaf temps -2,-3 cooler} that would be on the high end. do I keep the temp/RH or try to follow VPD. {just in flower}


what about if running CO2, and I am not, the last 2 wks before harvesting the RH should be between 40-30% 30% for the last week the VPD is at the high end of 1.6 When in that stage its at the right set of VPD just on the high or above set #…currently I am at 74 F- 37%RH and that gives me a VPD 1.5 in witch I am at a 1.57

 

[Arthur]

Depends on the chances of mold. If I had no mold issues I would follow VPD beginning to end. It is nothing more than themp/rH that gets the best growth... that does not take into consideration issues in different grows, or possible pathogens.

 

[Death The Cultivator]

Imo, running sub 40% RH is detrimental at any stage of life. I typically run 84-86f through flower and humidity remains around 55-65% RH.

If you measure out the progression from seed to to harvest, there's only about a 15% decrease in RH through the plants entire lifespan.

Are you measuring leaf temps as well? Do you have strong air circulation? Consistent conditions?

If you were running c02 there would be elevated humidity and temperature conditions but c02 would be cut off in the last two weeks.

 

[OG-GeMann]

Imo, running sub 40% RH is detrimental at any stage of life. I typically run 84-86f through flower and humidity remains around 55-65% RH.

If you measure out the progression from seed to to harvest, there's only about a 15% decrease in RH through the plants entire lifespan.

Are you measuring leaf temps as well? Do you have strong air circulation? Consistent conditions?

If you were running c02 there would be elevated humidity and temperature conditions but c02 would be cut off in the last two weeks.

You know what and you are right for most of the grow I kept it at 77-80 {no CO2} 50-60% RH...... I wasnt to sure about in the last weeks of flower ???? as of now its stable at 75F-37% RH and yes i take leaf temps. it falls to -3 cooler

 

[olbobcat]

Lets talk about VPD in flower, Am I supposed to follow VPD when in flower. (the final 2 weeks) humidity 30-40% temps 70-75F will give me a VPD of 1.5-1.65 {leaf temps -2,-3 cooler} that would be on the high end. do I keep the temp/RH or try to follow VPD. {just in flower}


what about if running CO2, and I am not, the last 2 wks before harvesting the RH should be between 40-30% 30% for the last week the VPD is at the high end of 1.6 When in that stage its at the right set of VPD just on the high or above set #…currently I am at 74 F- 37%RH and that gives me a VPD 1.5 in witch I am at a 1.57

View attachment 1299241

I was between 1.3 and 1.5 through second half of flower till end. I was very happy not to have any mold at 50-55 rh.

 

[Death The Cultivator]

You know what and you are right for most of the grow I kept it at 77-80 {no CO2} 50-60% RH...... I wasnt to sure about in the last weeks of flower ???? as of now its stable at 75F-37% RH and yes i take leaf temps. it falls to -3 cooler

The plant is still alive in the last weeks and imo this is equivalent to belief in needing to flush pre harvest. Uptake can be affected by low humidity and it all plays into your environment remaining stable consistently.

A poorly managed environment can cause mold where swings are prevalent in temperature and humidity. There are other ways but having strong air circulation, good housekeeping, VPD, will promote healthy plants that are even less susceptible to negative conditions in the environment.

 

[Mañ'O'Green]

@OG-GeMann Your plants are looking good.

There is science. There is Bro-science and there is Farming. VPD does not lie growing above 1.6 is not healthy for the plant. Many growers keep RH <40% in flower believing it will prevent bud rot. It sorta does but not for the reason they think. Because the plant stops growing that far out of VPD range the buds remain more open (airy) than they may have been. Denser buds are a lot more susceptible to mold. So that is an example of Bro-science. By the way genetics plays a big role in mold resistance. It has been my personal experience in Bud Rot that I allowed the dew-point to reach the ambient temperature during lights out. This allows condensation to form on the buds and remain where the airflow was inadequate.

A VPD of 1.5 should be OK. I live in a desert and often get out of VPD in the summer. Try not to let it get too much higher.

Then there is Farming and you are the farmer. Look at your plants they will show you what they need.