Other factors influencing light intensity besides season include the presence and type of curtains, the weather, shade from buildings or vegetation, the cleanliness of the window and the reflectiveness of the surroundings. Houseplant owners can compensate for low light intensity by increasing the time a plant is exposed to light. Increased hours of lighting allow the plant to make sufficient food to survive and grow. Additional light can be supplied from either incandescent or fluorescent lights or special horticultural fluorescent lights. Any type of light that burns a metal element, including the common household light bulb, is incandescent.
Florescent lights are cool or blue light.
By supplying a combination of incandescent and fluorescent lighting, most of the needed light spectrum is provided. A combination of fluorescent and incandescent lamps supplies the best light for houseplants, he said. However, using only cool white fluorescent tubes provides the best light for the money. Special plant growing fluorescent tubes make plant foliage and flowers appear more attractive, but they are more expensive than the cool white tubes, and in general, plant growth may be no better. Suspend fluorescent fixtures about 24 inches above the pots.