Jimster
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I have grown in relative humidity levels from as low as 10 or 15% in the winter,
Here is my opinion. VPD when used properly is very effective. This means taking leaf temp into account. So many people do it wrong. You MUST have good airflow throughout the plant.
Now in terms of differing experiences I have an answer to that and it's simple. The faster you plant is growing the more crucial each variable becomes. So in my sealed hydroponic RDWC, high light room with CO2 I find it makes a big difference whether I'm in the ideal VPD range or not. In a dirt grow without CO2 this variable become less of an impact and wider ranges will work without issue.
It's also an important factor in nutrient uptake so when we find what RH with how much light and how much nutrients works we stay with it. If you change the RH you are likely to see negative effects if we are not adjusting other variables that are affected by this.
Just my opinion. The importance is dependent on how we grow and how fast our plants are growing among a few other things I will just leave out.
Added: also in terms of mold with a higher RH. When the temps drop at night the humidity will often spike if this happens quickly. With a lower humidity this is not nearly as much of an issue. But if parameters are kept in check using VPD and good airflow mold should not be an issue. Also some genetics do better than others
High humidity has no place in a flower room, last 4-5 weeks I like to be 40-50%.
But I have noticed vegging plants seem happier with a bit higher humidity. I'm perfectly happy to concede I could be wrong, but understanding VPD was a pretty big part of the coursework when I was in school for greenhouse production horticulture. It might not be a super critical factor, but I do believe a tuned VPD does optimize growth rates. To what extent... We need someone to run side by side tests on this shit..
Here is my opinion. VPD when used properly is very effective. This means taking leaf temp into account. So many people do it wrong. You MUST have good airflow throughout the plant.
Now in terms of differing experiences I have an answer to that and it's simple. The faster you plant is growing the more crucial each variable becomes. So in my sealed hydroponic RDWC, high light room with CO2 I find it makes a big difference whether I'm in the ideal VPD range or not. In a dirt grow without CO2 this variable become less of an impact and wider ranges will work without issue.
It's also an important factor in nutrient uptake so when we find what RH with how much light and how much nutrients works we stay with it. If you change the RH you are likely to see negative effects if we are not adjusting other variables that are affected by this.
Just my opinion. The importance is dependent on how we grow and how fast our plants are growing among a few other things I will just leave out.
Added: also in terms of mold with a higher RH. When the temps drop at night the humidity will often spike if this happens quickly. With a lower humidity this is not nearly as much of an issue. But if parameters are kept in check using VPD and good airflow mold should not be an issue. Also some genetics do better than others
Sorry... I was talking about Relative Humidity, not Ph.Yes ph is a big deal, you want to get the most out of your plants right, you want to bring your plants to there full potential right? Do you want to be dealing with problems? And it's not like it's hard or even expensive, first you must understand ph in soil and what it means, a ph of 7 is neutral, cannabis grows best at around 6 to 6.5 max I'm not saying a cannabis plant won't grow with a ph of 7 or 5.5 but those are not optimal ph for cannabis, they are impeded from up takeing the proper nutrients needed to give you maximum flower production, is that not what you want for your plants? And for $15 I bought an electric ph meter so there is no excuse not to check just lazyness, I mean why wait for problems to start when you can avoid them altogether?
I often see the question posed about temps outdoor of 100+ and why indoor temps are an issue at that level. My thoughts on that are temps and humidity and other variables outdoor can reach extremes but in the scheme of things these periods are generally short enough that they don't usually affect the overall health of the plants. As is true with most questions about optimization of growing there is no one answer usually and it's the circumstances that dictate what the proper course of action is.Ok well i thought it was a misspell, yes you rel hum is important, I keep mine 40 to 50% max, high humidity makes your plants sweat under the lights stressing them and leavening them suseptable to mold, with high humidity often comes high heat witch stresses your plant more in severe cases leading to popcorn bud, friend the whole point of growing indoors is beacuse you can control your environment, even out of doors plants you need to find a strain that can handle the conditions, here we have many days above 90f a few days of 100f and dew points in the high 70s not many plants can handle this.
I often see the question posed about temps outdoor of 100+ and why indoor temps are an issue at that level. My thoughts on that are temps and humidity and other variables outdoor can reach extremes but in the scheme of things these periods are generally short enough that they don't usually affect the overall health of the plants. As is true with most questions about optimization of growing there is no one answer usually and it's the circumstances that dictate what the proper course of action is.
This is why this forum is so successful we have a ton of great growers with extensive experience in all sorts of different circumstances that collectively solve anything imo.
Great discussions that lead lead to real answers and while things may get heated from time to time we all get it done... Help new people and learn a metric shit ton from eachother.
Ok I'm going back to being a cranky old man now. That's about all the niceness I can put out in one day
The bests explanation on the effect of rh on plants I could find was plants work on hydraulics. With a high rh the plants needed water is absorbed through the leaves slowing down its need to draw water and nutrients from the roots leaving a build up of nutrients behind in the soil that then can lead to nutrient lockout.Recently I have seen a lot of posts about relative humidity and the importance of it being in the proper Zone. I have grown in relative humidity levels from as low as 10 or 15% in the winter, to as much as 80% in the summer, and I find that I see very little difference at all in yield or potency of the plants. They seem to react the same regardless, with the possible exception of when they first start I might see a little bit of tip Browning which quickly dissipates as the leaves fill in more. I grow mostly Sativa strains, so perhaps that has something to do with the lack of problems. In truth, my rh rarely goes above 30% and no issues seem present. Why do some seem to have problems... it seems higher Rh causes more problems, like PM and similar maladys.
What is your experience?
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