Houseplants, just like people, are affected by winter. Temperatures drop, humidity falls and the days get shorter, reducing the quantity and quality of available light. The change in light conditions can cause your favorite plant to suddenly drop leaves. Some varieties, such as figs and hibiscus can lose so many leaves that you may think they are dying.
Keep in mind that this is natural response to environmental stress. Be sure their winter home is away from cold or hot drafts, resist the urge to fertilize to help them snap out of it (it won’t), and watch them carefully to determine their watering needs. Most houseplants need to dry out a bit between waterings. Test by sticking your finger into the soil a couple of inches to test for dryness, and by watching for signs of wilt. Use plain water that has been allowed to warm to room temperature is the best choice during the winter. March is the time to start fertilizing your plants again. Use half strength until April 15, when you can return to full strength.