Houseplants don’t need as much water in winter

I keep plants in my office window through the winter and appreciate having them while outside, the garden is dormant.

During the winter, most houseplants are not actively growing due to short day lengths, reduced humidity, and lower temperatures (unless you are growing them in a greenhouse).

Generally, houseplants require less water and much less, if any, fertilizer because their growth slows during the winter. Different plant species need different watering frequencies, but most prefer to be watered when the medium is barely moist to the touch or almost dry. Ferns prefer to be kept more evenly moist, while succulents prefer to dry out more between watering. Water houseplants thoroughly when you do water them. Water should freely drain out of the bottom of the pot. If the excess water drains into a saucer, discard the water and replace the saucer beneath the pot.

Overwatering your houseplants encourages fungus gnats, which are a common pest of plants grown indoors, especially in situations where humidity and moisture are consistently high. The adult fungus gnat is a small (1/8-inch-long) dark, mosquitolike insect with long legs and one pair of clear wings. You usually first notice them flying around houseplants as the plants are watered or moved. The larvae feed on roots and can cause damage when populations are high. Look for sudden wilting, loss of vigor, poor growth and yellowing of foliage. Start to correct this problem by allowing the top couple inches of the growing medium to dry out before watering again.

Most houseplants perform well with daytime temperatures of 65 to 75 degrees Fahrenheit and night temperatures of 60 to 65 degrees in winter. Temperatures below 50 degrees or rapid temperature fluctuations may damage some plants. Keep houseplants away from cold drafts, radiators and hot air vents. Also, make sure houseplant foliage doesn't touch cold windows.

Houseplants with large leaves and smooth foliage, such as philodendrons, dracaenas and rubber plants can benefit if their leaves are washed at intervals to remove dust and grime. Cleaning houseplants improves their appearance, stimulates growth, and may help control insects and mites. Large, firm-leafed plants may be cleaned with a soft sponge or cloth and tepid water. Another method is to spray off the leaves in a shower.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.