Tips for Controlling Humidity When Growing Indoors
Many houseplants come from tropical and humid climates, so they prefer more humidity than temperate Mediterranean climates tend to have indoors. On the other hand, plants that grow natively in desert environments might occasionally require less humidity than levels that occur in many households. For the best plant health, take steps to control indoor humidity, which is especially important when you use artificial heat or air conditioning.
One of the most effective ways to increase humidity indoors is to attach a humidifier to your home's heating or ventilation system. You can also purchase free-standing humidifiers, although they take up more interior space. If you already have a modern heating system with a built-in humidifier, make sure to keep its water levels full. Most houseplants prefer humidity levels above 40 percent. Although you want the humidifier to sit in the same room as the plants, it is also helpful to keep plants away from vents that release cold or hot air.
If you do not have access to a humidifier, increase humidity around houseplants by promoting water evaporation near the plants. Placing plant pots on a tray of moist pebbles increases humidity around the plants. You may also place open jars of water among plants so they can take advantage of the evaporation. Occasional misting with a spray bottle also slightly increases humidity, but too much misting contributes to fungal diseases. Limit misting frequency to twice per week or less, and do not mist plants with hairy leaves that can prevent evaporation.
Placing potted plants in groups increases relative humidity near the plants because plant leaves give off moisture. Rooms with frequent warm water use, such as bathrooms and kitchens, also tend to have higher humidity levels than other rooms in the house. Keep plants away from wood-burning stoves and other sources of heat that may reduce humidity. Greenhouses also tend to have higher humidity levels.
If you have problems with indoor mold and plant fungal diseases or if you are growing plants from very dry climates, you may need to decrease your home's indoor humidity. The U.S. Environmental Protection Agency recommends fixing all moisture leaks in the house, such as leaky pipes, to reduce indoor humidity. Dehumidifiers also help. During or after showering or doing dishes, you can also reduce humidity by turning on exhaust fans or improving ventilation with open windows. Fans and open doors throughout the house also decrease humidity by improving air circulation and reducing condensation.
- University of Illinois Extension: House Plant Care
- University of California UC Master Gardener Program: Indoor Plants
- The University of Georgia College of Agricultural and Environmental Sciences: Growing Indoor Plants with Success
- Purdue University Cooperative Extension Service: Indoor Plant Care
- Chicago Tribune: Indoor Plants Need Lots of Humidity During Winter Months
- Weather Channel: Controlling Indoor Humidity
- United States Environmental Protection Agency: Mold Resources
Lisa Chinn developed her research skills while working at a research university library. She writes for numerous publications, specializing in gardening, home care, wellness, copywriting, style and travel. Chinn also designs marketing materials, holds a Bachelor of Science in psychology and is working toward a PhD in cognitive neuroscience.