By Bob Westerfield
University of Georgia
Temperature level essentialFirst, consider the temperature. Many container plants live on outdoor porches during the summer and early fall months. As temperatures dip to 50 degrees or less, plant owners begin to move plants indoors. The best way to protect outdoor potted plants is to first bring them into a garage or basement that is a little warmer than the outdoors, but not as toasty as inside the house. If the plants are moved immediately from 50 degrees to 75 degrees, some may become stressed and suffer. Plants should be acclimated slowly by a gradual increase in temperature. After a week or two, bring the plants into the warm house. Most house plants grow best in daytime temperatures between 65 degrees and 75 degrees and nighttime temperatures between 60 degrees and 65 degrees. To further protect them, keep houseplants away from cold, drafty windows or hot radiators, stoves or air vents. Also keep houseplant foliage from touching cold windows. This can burn the leaves.
High humidity bestHumidity is important. Most houseplants prefer a humidity level of 40 percent to 50 percent. The relative humidity in most homes is closer to 15 percent – a level much too low for most houseplants. Raise humidity levels by using a humidifier or grouping plants together. Placing houseplants on saucers filled with gravel or small pebbles and water will also increase humidity. The bottoms of the pots should always be above the water level. Don’t mist houseplants in an effort to raise the relative humidity. Misting would have to be done several times throughout the day to have any real affect.
Water, but not too oftenIn general, houseplants don’t require as much water during the winter months. That doesn’t mean they can be completely ignored. The type of houseplant and soil will determine the water needs. Ferns prefer evenly moist soil and fairly frequent watering. Cacti and succulents should only be watered when the potting soil becomes completely dry. Most houseplants fall somewhere between these extremes and should be watered when the soil is barely moist or almost dry to the touch. When watering, apply a thorough amount. Water the plant until water drains out of the bottom of the pot. Be sure that plants have good drainage. Never allow plants to sit in excess water unless the pot is placed on gravel to raise humidity.
Clean but don't fertilizeDrastically reduce or eliminate fertilizer during the winter months since most plants grow very little. Fertilize again in late March or April as growing conditions improve and the plants begin to flush out. It’s important to keep houseplants clean while they rest through the winter. Grease and dust can accumulate on leaves and slow down the normal transpiration. Cleaning houseplants also improves their appearance, stimulates growth and can help control insects and mites. Large, firm-leafed plants can be cleaned with a soft sponge or cloth dipped in a mild solution of dishwashing soap and lukewarm water. Leaves can also be cleaned by placing the plants in the shower under lukewarm water.
(Bob Westerfield is a Cooperative Extension horticulturist with the University of Georgia College of Agricultural and Environmental Sciences.)