Effects of Low Humidity

I live in the North and am growing in a basement. The lights and a supplemental heater are keeping the temperature ok, but even with 2 humidifiers in an 8 foot square room, I can’t get the humidity much over 35%. The plants are in veg and look fine, but I’m curious to know effects of low humidity throughout the life cycle of growth. The only thing I have noticed is that the leaves look wider than expected for a white widow strain. I thought it was sativa dominant, and therefore, would have narrow leaves. Photo at week 3 attached.


Light could be a little closer, the leaves are reaching for the light, just imo


I agree. I left town for 4 days and adjusted the light up and soaked them with Flower Power Grow from the kit of WW autoflower I bought from this great site. They survived. Both humidifiers ran dry, but even full and wide open I can’t seem to get that humidity up.

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@tjfrombama, have you try the hanging damp/moist bath towel trick with a fan aim at it ? Or a couple of bowl of water ? Low tech but it work ! :grinning:

~Al :innocent: :v:


Can you slow your exhaust fan down if you using one
And how big of one do you have if you are using one

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No exhaust fan yet. I would never keep the room heated if I drew in cold air from the rest of the basement. However, there is a central heat register in the room, so I’m sure it is blowing in warm air and forcing air out. Maybe I could shut it down. The lights and a portable heater keep it plenty warm. I sure would like to know long term effects of low humidity throughout the grow cycle. I’m sure as it gets warmer outside, this problem will go away. But, a whole winter cycle will probably be low humidity for me. I will try the towel trick tonight. Thanks.

The short and medium term effects of very low humidity (under 30%) on a plant is a stunt in growth and signs of underwatering (leaf dropping) Why? Because the plant will protect it self in closing her stomata (tiny little hole under the leaves for gas exchange) and stop “breathing”, mater of speak, trying to keep humidity in.

I am apologise for not answering the main question earlier, I simply mist the main title :innocent:, so, at 35% of humidity, they will probably have the symptom in the early and late day light schedule.

Hoping that now I respond to your question @tjfrombama to your expactation :slight_smile:

~Al :v: :innocent:

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Maybe you can consider Co2 being that it’s helps moisture in the air which can add to your humidity, but even at your numbers I’ll leave it alone they will do fine at 35% .

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8 foot square without a CO2 generator is feasible, good point @yoshi :+1:

But I disagree to let them along at this young stage (first 2-3 nods, fourth nod just pointing)

Nothing personnal (you know I respect you, yoshi)

Ideal humidity at that stage is between 50-55 % , aim for 45-50 % for now and for vegetative stage. Between 40 to 45 % in flowering stage and end off, for riping flowering stage at 35-40%. @tjfrombama

Hoping that’s helping you :innocent:

~Al :v: :innocent:

That’s could be hurting you if you have forced warm air it dries out the air
You should look into a whole house humidifier and since you have a duct in there putting one on heating system would do the whole house which is just healthier for you
But if you can’t do that a free standing whole house would work

Technically you correct but if the grower cannot afford the right equipment to manage his grow space due to lack of finances than its only so much can be done, DIY options etc, but with that much open area I think they will do okay but I’m no expert just my opinion but Co2 always help me raise my humidity cause I have a lot of led power in a small space.


Thanks so much for all of the valuable information. This is a great community. When I got home, I noticed roots starting to poke out of the bottom openings on some of the pots. So, I transplanted to 5 gallon fabric pots of Foxfarm Ocean Forrest. Put 5 quarts of water in each pot and rinsed and filled the under the bed storage tote that was holding the 1 gallon pots with water. Now, humidity at 60% but temperature dropped to upper 60s. I think I will be able to dial it in now. Thanks again.

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