University of Vermont Extension 
Department of Plant and Soil Science

Winter Article


By Dr. Leonard Perry, Extension Professor

Cold weather means that most folks have their homes closed up and the heat on.  After a while, the lack of moisture in the air becomes quite noticeable to the occupants, especially the houseplants.  For those plants that prefer a high level of humidity, the low humidity commonly found in homes in winter can be a shedding experience as their foliage yellows, dries up, and falls off.

Houseplants do best at a relative humidity of 70 to 80 percent, a level that is often difficult to maintain in the home.  Any increase in humidity will help plants, however, especially if the dwelling is heated by a wood or coal stove or fireplace.

One way to help increase the humidity around plants and keep them healthy and growing is to use humidifiers when available and practical.  It's also important to avoid raising the air temperature too high.  With a given amount of water in the air, the higher the air temperature, the lower the relative humidity.

An inexpensive way to raise the humidity is to place pans of water on stoves or radiators to act as humidifiers.  A gravel-filled tray partially filled with water also works well.  Just place your potted plants on top of the gravel.  The humidity will be increased in the immediate area of the plants.  But do not allow the bottom of the pot to come in contact with water as this can lead to a waterlogged soil ball that could kill the plant.

Move humidity-loving plants to the kitchen or bathroom.  These rooms usually have higher humidity than the rest of the house.  Or make a grouping of plants.  This will form a microclimate with a higher humidity.  And keep plants, especially ferns, away from wood stoves, fireplaces, and heat registers.

Many people mist their plants.  This is okay, but avoid prolonged misting.  A film of water on the foliage is often all that various fungus spores need to germinate.

A general rule of thumb to follow if you don't know the humidity requirements of a plant is that the lower the light requirement, the higher the humidity requirement.

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