Whether your houseplants summered outside or you want to overwinter special tropicals, the following tips can keep your plants in good shape:
Choose well
Not all plants do well indoors. While you may want to bring in all of your favorites, factors such as low humidity and low light can keep plants from surviving indoors the entire winter. Consider the plant's growing requirements and your available indoor conditions before deciding which plants to bring indoors.
Acclimate them
Indoor conditions are generally quite different from those outdoors. There is less direct sunlight, less air movement, and a lower level of humidity. To reduce shock experienced by your plants when you move them, acclimate them gradually to their new environment. For instance, if your plants grew outdoors in full sun, move them to a shady spot for a couple of weeks before you bring them in. If the plants grew in a shady spot, move them inside for a few hours a day, then increase the amount of time they're in until you no longer bring them out. Then be sure the spot inside has plenty of light.
Cut them back
Once your plants are ready to move indoors, it helps to cut many of them back slightly (by as much as a quarter, depending on the plant). Cutting them back stimulates the new growth that will adjust to indoor conditions. Much of the old foliage may drop from the plant.
Watch for insects
As you move your plants inside, look carefully for pests such as spider mites or whiteflies. It's helpful to examine plants with a magnifying glass. To help remove either insects or their eggs from a plant, wash the plant well with room-temperature water before bringing the plant inside. Wash both the tops and the bottoms of the leaves. Many insects hide on the leaves' undersides.
Site them well
Choose a brightly lit spot that's protected from hot and cold drafts. It's best to keep the plants cool, too. While you might want the inside air at 75ºF, it may be too warm. Most plants prefer daytime temperatures of 70ºF or less and 55 to 60ºF at night.
Water properly
During the winter, days are shorter and there's generally less light, so most plants will rest till early spring. Therefore, only water them when the soil feels dry to the touch, but before the foliage wilts. Don't worry about fertilizing most indoor plant much until the days get longer and plants start to put on new growth next February, March, or April.
Boost humidity
In most homes, the amount of relative humidity is dangerously low for plants. Brown leaf tips or edges are often a sign of low humidity levels. To encourage enough humidity for your plants, site them close together (they give off moisture as they breathe) or set them on oversize trays of sand or pebbles. Fill the tray with water so the bottom of the pot sits above the water line. As the moisture in the tray evaporates, it goes into the air and is available for your plants.
While many gardeners believe that misting their plants helps, it's not a good long-term solution as it only adds moisture for a short time. As soon as the mist evaporates, it no longer adds to the humidity.