During the winter, most houseplants are not in an active growth phase 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 down during the winter.
Flowering houseplants such as African violets and hibiscus will benefit from fertilizing once a month in the winter.
The plant species will also affect frequency of watering but most prefer watering when the medium is barely moist or almost dry to the touch. 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 bottoms of the pots. If the excess water drains into a saucer, discard the water and replace the saucer beneath the pot.
Most houseplants perform well with daytime winter temperatures of 65 to 75 degrees and night temperatures of 60 to 65 degrees. 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 occasionally 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 the shower.
• After Christmas, your live cut tree can be moved outside and be redecorated for the birds.
Anchor the tree in a bucket full of damp sand or tie it to a fence or tree. Add strings of popcorn and cranberries. Apples, oranges, leftover bread and pine cones covered with peanut butter and then dipped in birdseed can also be added. For best results, push the edible ornaments well into the tree so that they do not blow off as readily.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.