Audrey Cooke
Frederick County Master Gardener

Here we are in mid-Winter and my houseplants have the "Winter Doldrums." Chances are your houseplants are also affected. If your houseplants have yellowing, wilting, mite infestation, loss of foliage, and are just plain sad looking, your houseplants too, have the "Winter Doldrums."

My green indoor friends, my houseplants, are currently huddled in two corners of my dining room, one corner of my living room and by the patio door in the kitchen area. They are really rather sad. The ones by the patio door seem to be looking out and thinking, "isn't it time for us to go outdoors yet?"

With houseplants, the key to surviving the winter months is not so much the moisture in the soil, though that is important, but the moisture in the air. With sufficient humidity, most houseplants achieve a measure of health; without it they grow sad. Until spring, what houseplants need is humidity.

A home with forced-air heating may have an automated humidifier integrated into the duct work, but keeping relative humidity at an optimum 50-60 percent, needed for healthy houseplants, is very difficult. Low humidity in most of our homes during the winter months is a given. The already low humidity of the dry winter air is pushed lower by the heated air in a home.

Here are a few of the options for raising the humidity in our homes for our houseplants.

Spray Misters

One impulse is to mist with a spray bottle, the plant and the air around it. This will work, but how many of us are going to do this on a daily and continual basis. The occasional misting just will not work. In greenhouses with continual spraying, misting keeps the humidity levels high, but odd squirts from a spray mister are not going to do much.

Water Trays

These can be an effective method of raising the humidity. Set underneath planted pots, they allow the water to evaporate into the air around the foliage. You fill the tray with gravel, which increases evaporation and raises the pot above the level of the water. Without gravel, the pot sits directly in the tray and the water wicks into the soil, keeping it too wet which promotes root rot.

Humidity Trays

For smaller plants, bonsai's, African violets and orchids, these trays can be very effective. Larger pots will probably benefit most from water trays. Humidity trays have a plastic grid that keeps the pots dry and they are readily available through most garden supply catalogues and garden centers. The cost for these trays are relatively inexpensive, usually $25 or less.

Portable Room Humidifiers

Cool Mist - Cool mist humidifiers, now on the market have thick pads that wick cold water while an impeller blade blows air over them and humidifies the room.

Warm Mist - Warm mist humidifiers are also available. They are not as popular as cool mist models because consumers fear that a warm mist conveys mold and bacteria. The manufacturers of warm mist humidifiers claim that this concern is unfounded; the heating kills the pathogens.

Ultrasonic Wave - A third type of humidifier uses ultrasonic sound waves to send microscopic droplets into the air. The Ultrasonic is not as popular because it generates a white dust.

All three humidifiers identified above are different from vaporizers, which saturate the air for people with respiratory ailments. When it comes to humidifiers, the cool mist seems to be most popular.

The worst problem we encounter in winter from our dry humidity is the worsening of pest problems. Mite populations build when hardy plants are subjected to hot, dry conditions in summer. The reasons for mite problems indoors in dry conditions are not well understood. One theory is that dry plants are not producing new growth and the mite damage does not get repaired.

Pest problems also arise because we tend to overfeed our plants in winter and mites, mealybugs, and scales also enjoy a nitrogen fix. So, keeps your plants humid, starve them a little bit, turn down the thermostat a few degrees, and keep the hope, spring is coming.

Read other articles on care of house plants

Read other winter related gardening articles

Read other articles by Audrey Cooke