Grow Room Humidity Too Low? Signs and Solutions
Most guidance obsesses over high humidity, but winter heating and hard-running exhaust fans routinely push tents down to 25% RH, which stalls growth just as effectively.
What low humidity looks like
Leaf edges curling upward and inward, crispy margins on otherwise healthy green leaves, pots drying out in under a day, and a plant that drinks constantly but grows slowly.
Fixes in order
Slow the exhaust fan down — often the whole problem. Add a humidifier outside or inside the tent with a controller. Place open water trays in the airflow path. Reduce the intake of very dry room air by conditioning the room instead.
Do not overcorrect
Raise humidity in steps of about 5% and hold for a couple of days. Slamming a flowering tent from 30% to 60% invites mold faster than the low humidity was hurting you.
Frequently asked questions
- Is low humidity ever good?
- In late flower, 45-50% is the target, and dropping slightly below that in the final week is generally safer than being too wet.
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