What is the ideal humidity level for leafy greens?


I’m growing leafy greens in my hydro system in my basement. What is the ideal humidity level and what is the best way to control it? Thanks.

Preston C.


Hi Preston,

Thank you for your question. The ideal relative humidity for growing leafy greens is 50-70 percent. To prevent mold and mildew from becoming an issue in your basement, home experts recommend keeping your basement between 50-60 percent.

It is crucial to maintain the proper humidity when growing leafy greens. High humidity levels can cause powdery mildew and tip burn. When humidity is too high, it causes transpiration to occur more slowly, which in turn slows the absorption of calcium. This calcium deficiency causes tip burn.

Low humidity can cause an outer leaf edge burn. This is a physiological disorder where lesions develop on the veins on the outer edge of the leaves. It is caused when sap exudes from the veins and then re-absorbs, creating a salt buildup.

It is also important to keep your humidity level consistent. Rapid changes in humidity can stress your plants and cause tissue damage because the plant doesn’t have time to adjust to changes in the environment. Rapid changes usually happen when you flood the room with dry outdoor air or from a sudden change in temperature.

When controlling humidity, keep a few key points in mind. Cooler temperatures increase humidity, while warmer temperatures decrease humidity. The water from your hydro system may increase humidity through evaporation, depending on the type of system you’re using. The more plants you have, the higher your humidity levels will be due to transpiration. If you are exchanging your air, the humidity level of the outdoor air you are bringing in will influence your indoor humidity level.

A dehumidifier is going to be the best piece of equipment to control humidity. Most dehumidifiers can be set to maintain your humidity at the level you choose. Keep in mind a dehumidifier will create heat in your room. While this may be good for burning off excess moisture, the heat from all your grow equipment can generate too much heat, in which case you’ll need to find a way to lower the temperature in your growroom. You can do this by exchanging indoor and outdoor air with exhaust fans, or by adding an air conditioner to your room. If you exchange your air, be mindful of the temperature and humidity outdoors, and how that may affect your indoor environment. These factors are constantly changing, and you’ll need to make adjustments regularly to balance them so your humidity remains consistent.

Good luck and keep growing!
Monica Mansfield

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Written by Monica Mansfield
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Monica Mansfield is passionate about gardening, sustainable living, and holistic health. After owning an indoor garden store for 5 1/2 years, Monica sold the business and started a 6.5-acre homestead with her husband, Owen. She writes about gardening and health, as well as her homestead adventures on her blog at thenaturelifeproject.com.

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