Indoor Plant Light Levels
Houseplants are outdoor plants being grown indoors. Direct or indirect sunlight is the best light for your houseplants, it has the balance of wavelengths necessary for health growth and flowering. However, some houseplants will grow very successfully in artificial light and artificial light can supplement natural light in dark areas of a house or office.
Plants need blue light for growth of foliage and red for flowering and fruiting. Green wavelengths are largely reflected which is why most plant leaves are green.
Incandescent light bulbs give warmer red wavelengths and can be used to supplement bluer light from fluorescent bulbs. The ratio of 1 incandescent to 2 florescent bulbs will give best results.
Newer LED bulbs are low heat, energy efficient and are available in wavelengths specific for indoor plants. General purpose white LEDs provide good supplementary light with some sunlight.
The use of artificial lighting can lengthen the day for plants. Plants slow growth in response to shortening days and daylight in winter. Day length may be more important in slowing growth than reducing temperatures. You can artificially lengthen the day by use of artificial lighting.
Artificial lighting can also be used to artistic effect in lighting your houseplants so that the plant is a feature in your home or workplace. In this case the lighting will be more subtle than the lighting required for growing.