In winter the level of illumination near the windows is very low. Indoor plants that grow near a sunny east or north window in summer and may need a south or west exposure in winter. Likewise, plants near west or south windows that need filtered light in summer can tolerate direct sunlight in winter.
How to help your plants deal with changing light levels:
1. Move the plants as close to the windows as possible.
2. Clean windows to ensure maximum light transmission.
3. In winter, move the plants to new locations next to the lighter windows.
4. Remove dust from the plants so that the leaves can have the most of the available light.
5. Add artificial light. Fluorescent lamps provide sufficient illumination. Position bulbs 4 to 12 inches from plants for effective results.