Mephisto Genetics Mephisto genetics customer service/feedback thread!

[stan_mephisto]

Do you mean dialing in temp and RH to a good VPD value means you run the risk of mold because you're basically in the 60s to 70s for RH?

No, the opposite. But other factors are in play for potential to get bud rot, plant health being one of them.

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[lunarman]

No, the opposite. But other factors are in play for potential to get bud rot, plant health being one of them.

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Stan, I'm experimenting with VPD right now and I find my plants are the most healthy ever. Learning lots. Learning what I can do in my tent with temp and RH so they are a good value on the VPD chart. I have seen no issues so far. On day 38 right now so transitioning to flower is on. During seedling and veg over first 30 days temp was on average 74 and RH was 60%. I had to put a big humidifier in my tent to achieve this. Now the plants are transpiring a lot and I don't need a humidifier in the tent. I need a dehumidifier and that's working great. I set it to 60% and just adjust my temps so VPD is a good value.

Do you reduce your temp and RH during flower but still maintain a good VPD value? Or do you use the same temp and RH as you did in seedling/veg?

 

[stan_mephisto]

I bring the temp and humidty down, my humidty stays pretty constant once they are large and transpire a lot. I also adjust the flow on my exhaust to tune in the vpd without a dehumidifier.

Take everything i say with a grain of salt though lol. I do lots of research and implement it into my garden, but im not very good and reteaching it to others, thats why I posted my favorite podcast. Lots of great info in there from leaders in the industry.

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[lunarman]

I bring the temp and humidty down, my humidty stays pretty constant once they are large and transpire a lot. I also adjust the flow on my exhaust to tune in the vpd without a dehumidifier.

Take everything i say with a grain of salt though lol. I do lots of research and implement it into my garden, but im not very good and reteaching it to others, thats why I posted my favorite podcast. Lots of great info in there from leaders in the industry.

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I can relate to that caveat and I will check out the podcast you linked.

 

[Simplicio]

Stan, I'm experimenting with VPD right now and I find my plants are the most healthy ever. Learning lots. Learning what I can do in my tent with temp and RH so they are a good value on the VPD chart. I have seen no issues so far. On day 38 right now so transitioning to flower is on. During seedling and veg over first 30 days temp was on average 74 and RH was 60%. I had to put a big humidifier in my tent to achieve this. Now the plants are transpiring a lot and I don't need a humidifier in the tent. I need a dehumidifier and that's working great. I set it to 60% and just adjust my temps so VPD is a good value.

Do you reduce your temp and RH during flower but still maintain a good VPD value? Or do you use the same temp and RH as you did in seedling/veg?

I've been using the VPD chart for a couple years in DWC, and the biggest problem i've seen is too much growth.
The plants love the high humidity VPD calls for, but they can become uncontrollably tall.
The only concession I make to bud rot warnings is to keep the humidity in the lower 60s instead of the upper 60s, after subtracting 5-7 F from air temp to get leaf temp.

Most of the VPD advice I've seen says to reduce humidity during flower, but I suspect that is reverse engineered to not stray far from the accepted wisdom that low humidity is needed in flower to avoid bud rot.
So far no rot, but being in DWC might help prevent it.

 

[lunarman]

I've been using the VPD chart for a couple years in DWC, and the biggest problem i've seen is too much growth.
The plants love the high humidity VPD calls for, but they can become uncontrollably tall.
The only concession I make to bud rot warnings is to keep the humidity in the lower 60s instead of the upper 60s, after subtracting 5-7 F from air temp to get leaf temp.

Most of the VPD advice I've seen says to reduce humidity during flower, but I suspect that is reverse engineered to not stray far from the accepted wisdom that low humidity is needed in flower to avoid bud rot.
So far no rot, but being in DWC might help prevent it.

I am not getting too much height using VPD sweet spot. My plants are on day 37. My tallest (autos) are 29 inches right now and no more stretch happening. But I am getting a lot of leaf growth while transitioning in to flower. But not sure that is happening more because of good VPD. I think it is.

I read one long thread on another board where the OP grew in the tropics for years and basically was mastering high RH grows. Turns out it was VPD but I don't think he realized it at the time but does now. And now his indoor grows are all done with higher RH and proper VPD values. And he has RH at 70% in flower and says its the best. Just need lots of air circulation. I saw the pics of his indoor grows and they were top shelf, larger scale.

I'm going to keep my RH at 60 for the duration of the grow and temps will fluctuate a bit between day and evening. Dont think I want to try 70% during flower, but 60% is doable. I wasn't using leaf temp in my VPD chart lookup though. I was using air. I need to check that out. If my leaf temp is that much lower then I might not be in the VPD sweet spot. But I think its ok still. Thanks for mentioning the leaf temp.

And I also think the lower RH during flower isn't actually ideal for best product. I think its to prevent mold.

 

[stedimed]

Last grow I really tried applying VPD to it and saw stellar results to previous. In veg. 60'-low 70's depending on temp. then dropped accordingly in flower per chart. I even used laser temp gun to monitor leaf and soil temp. For me I think it may have boiled down to not quite enough air flow, consantly trying to tweek it, hard to get ideal in all spots at one time. Then removing a fan for a bit was a brain fart, I feel now like what was said,when growing within VPD ideal range with the higher RH, air flow is critical. It was the only affected with great results throughout. I'm a little paranoid now with it and shouldn't be as I have good air on the single going.

 

[lunarman]

Last grow I really tried applying VPD to it and saw stellar results to previous. In veg. 60'-low 70's depending on temp. then dropped accordingly in flower per chart. I even used laser temp gun to monitor leaf and soil temp. For me I think it may have boiled down to not quite enough air flow, consantly trying to tweek it, hard to get ideal in all spots at one time. Then removing a fan for a bit was a brain fart, I feel now like what was said,when growing within VPD ideal range with the higher RH, air flow is critical. It was the only effected with great results throughout. I'm a little paranoid now with it and shouldn't be as I have good air on the single going.

Great read. Good to see someone reporting positives back on switching to ideal VPD. I love it too. I am running two big oscillating fans on 10 plants constantly. And I think another thing is with VPD you get lots of veg growth so you might have to strip out fans around days 30-40 on the inside of the plant when they get really bushy so the air can get in there.

Did you have bud rot or mold? You didn't have ideal results in the end?

 

[stedimed]

Great read. Good to see someone reporting positives back on switching to ideal VPD. I love it too. I am running two big oscillating fans on 10 plants constantly. And I think another thing is with VPD you get lots of veg growth so you might have to strip out fans around days 30-40 on the inside of the plant when they get really bushy so the air can get in there.

Did you have bud rot or mold? You didn't have ideal results in the end?

Well when I took off top and started trim, kinda pulled her apart to trim fans left and found white fur throughout. No where else anywhere. But yeah overall great results for me and past grows! Again I don't think I can say I'm fully implementing VPD as far as the air flow concerns. THAT will be taken care of in the future.

 

[lunarman]

Well when I took off top and started trim, kinda pulled her apart to trim fans left and found white fur throughout. No where else anywhere. But yeah overall great results for me and past grows! Again I don't think I can say I'm fully implementing VPD as far as the air fow concerns. THAT will be taken care of in the future.

Here is my answer for air circulation in my 8x8. Opposing oscillating fans in the middle of the tent. Been watching the leaf movement with various fan configurations and this gives the best circulation. The plants are along the walls of the tent and the fans in the middle!