If your houseplants spent the summer outside or if you want to overwinter special tropicals, follow these tips to keep your plants happy until spring:
Not all plants do well indoors. 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.
Hibiscus, citrus, cordyline, phormium, palms, croton, bamboo, jasmine, allamanda and bougainvillea can survive, if not thrive, when overwintered as houseplants, according to gardening expert Kathleen LaLiberte. Brugmansia, banana and dwarf canna, however, are best kept as dormant plants in a cool, dark place. And begonia, dahlia, ginger, sweet potato vine, colocasia, caladium, canna and calla should be stored as dormant bulbs and tubers, also in a cool dark place.
Site them right
Choose a brightly lit spot that's protected from hot and cold drafts. Then try to keep your house as cool as you can tolerate it. While you might want the inside air at 75ºF, most plants prefer daytime temperatures of 70ºF or less and 55 to 60ºF at night.
Watch for insects
Before 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 remove insects or their eggs from a plant, wash it well with room-temperature water before bringing the plant inside. Many insects hide on the leaves' undersides, so wash both the tops and the bottoms of the leaves.
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 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.
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.
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 becomes 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.