Humidity during grow

Hey guys , I'm just wondering how crucial it is to watch humidity during grow ? I read this article that stated the humidity should constantly change as the plant is in different stages. Is this true? Or is there just some average humidity you can keep it at the entire life cycle? Thanks !

Where I live, it’s dry, like it can be 20% in the winter. And summer can get to be 70% or more. But I think it matter more if you live in a very humid area, then you have to be careful.

Temp and rh combined are going to dictate the plants metabolism.....i.e. how fast it drinks, and consume nutrients. 50-60%, depending on temp, is a decent average.

Look into vapor pressure deficit.

Fancyhuh101 said:

Hey guys , I'm just wondering how crucial it is to watch humidity during grow ? I read this article that stated the humidity should constantly change as the plant is in different stages. Is this true? Or is there just some average humidity you can keep it at the entire life cycle? Thanks !

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Yes, true, at least in an ideal envi. Generally speaking, humidity should decrease as the grow progresses. Sprouts and vegetative plants like higher humidity. As things start to get more dense in the growth, you want to decrease (and provide circulation) to avoid mold and other issues. By later flowering, humidity should be below 50%, ideally, to avoid mold concerns.

Edited to add: and as pointed out above, temp is really important as well. VPD.

Thanks for the reply guys !

VPD 1.2-1.6 is a safe range, going up to 1.6 starts pushing it. Make sure to research Leaf Surface Temp too. I like a 1.3-1.4 VPD in veg/bloom.

I have grown in fairly humid environments and air circulation and exchange are really important. If you're having 80% humidity during veg as long as you have moving air so the leaves aren't touching. During flower humidity like that can be a problem for many strains with dense buds. Low humidity conditions can stun plant growth during veg and require more or less fertilizer depending on strain. Last winter I switched from a 600 hps/mh to an 620 led. My humidity went from 45% to 65% or 75% and it made a huge difference with my water usage. I was watering every 2 or 3 days with it at 45 and it went to 4 or 6 days with the extra 20% humidity. I'm running co2 with a generator so the extra bit of humidity really helped with the last crop.

Thanks for the link, VPD wasn't really a thing or widely discussed a decade ago. Either that or I've completely forgotten about it. Which is also highly likely as I bounce hobbies.

D3monic said:

Thanks for the link, VPD wasn't really a thing or widely discussed a decade ago. Either that or I've completely forgotten about it. Which is also highly likely as I bounce hobbies.

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key is knowing ur top sea of green canopy vpd vs overall enviroment. Intill I did that I thought I had certain things like rh/temp and my vpd in proper range. having a monitor made all the difference to make you aware 24/7 but also alert you if off from rh,temps,co2 and vpd

Either over crowding/lack of air flow, high RH%, dying leaf tissue or all the above caused mold to grow into an entire plant of mine in less than a few weeks. Right before chop.

I was reading that keeping RH% below 45% was a good measure but lately I am seeing grows that grow above that without a dehuey that gets no mold.

Either way I know it is critical to try and keep up with all I mentioned as I was denied an entire yield over it and am starting over.

Which one is less critical than the other, idk so I am asking along with you and watching for feedback.