Humidity and House Plants

Relative humidity is a measurement of the percentage of moisture in the air. Many houseplants originate from tropical regions, and as such are adapted to live in high humidity levels. Most houseplants have evolved in environments with humidity levels reaching 80%. However, the average home environment has only about 30% humidity. In winter months with home heating systems, the relative humidity in the home may drop even lower.

With low humidity, plants may not be able to adequately replace moisture lost through their leaves through transpiration. One sign of low humidity induced stress in houseplants is brown tips on leaves.

Tolerance for low humidity varies by individual species. For instance, some houseplants will do fine in average home humidity levels. However, other plants require higher humidity levels for optimum health.

Below are some suggestions for raising the humidity levels around your houseplants:

1. Add a humidifier to the room à Humidifiers add water to the air, and raise the humidity in a room. This will make the room more comfortable for both plants and people. Humidifiers are especially helpful for the dry winter months.
2. Group plants together à Plants release water from their leaf stomatas during transpiration. This creates a layer of moist air around a plant, which can benefit surrounding plants.
3. Use a pebble tray à To make a pebble tray, place plants on top of a tray filled with pebbles or marbles. Then fill the tray with water, making sure that the plant rests atop the pebbles and is not sitting in the water. As the water in the pebble tray evaporates, it will raise the humidity level around the plant.
4. Mist plants frequently à By spraying water on the plants leaves with a hand-held mister, you can temporarily increase the humidity around plants. But note that the effectiveness of this method can be debated.

Written by Adrienne Kleintop