Even with the unseasonably warm weather we were having, you really should have brought your tropical houseplants inside already. That is the easy part,
now let's learn how to keep them happy and healthy all winter.
Look for pests.
Ideally this should have been done before you brought them in. But it's fine to spray both the soil and the entire plant (leaves, stems, etc.) with insecticidal soap
Redo this in January or as needed.
Fertilize at half strength
Read the package directions and cut in half and feed less often. A water-soluble fertilizer is fine or use a compost tea brew.
Foliage plants are easy
Easy care plants that do best indoors are generally varieties prized for their foliage and these can handle lower light conditions indoors.
Tropical flowering plants are more challenging
Some varieties, which require a lot of light, include Hibiscus, Mandevillas, Jasmine, Bougainvillea and Citrus. They require a sunny window in a room where air temperature stays about 60-70 degrees and a humidity level between 30 and 45 percent (mist leaves or place a pan of water among the plants).
You have two options:
Let them go dormant. If you plan to let your plants simply go dormant, let them rest in a cool place such as an unheated basement or garage (40 to 50 degrees F) with little or no light-their leaves will gradually yellow and drop. Water sparingly - about twice per month. Bring them out in early spring and start watering.
Coax a few blooms out of them, while inside. Know that growth and blooms on overwintered tropicals will appear later in the season. Water carefully. Often our heated homes become quite dry, which can cause plants to lose moisture quickly. However, plants aren't actively growing during the winter months so they don't require as much water. Test the soil using the tip of your finger, if the top inch is dry go ahead and water. Practice makes perfect. Good luck