Light affects the quality of plant growth, development and longevity. Without light, even the hardiest plant will die. The best light for plants is the sunlight, which produces all of the colors of the spectrum. Plants can use any of these colors it needs most at any given time.
The amount of light and the cycle of light and dark periods of the day affect the flowers of plants the most. Long periods without light will prohibit many plants from flowering, hence the winter hibernation of most flowering plants. A few plants are "day neutral" and will flower regardless of the amount of light available. These plants include poinsettias and tomatoes.
Light influences the direction a plant grows. It will bend toward a light source. The action of seeking light is called phototropism.
Photosynthesis is the method of turning light into energy. It is the way plants absorb light for food and covert its nutrients into vital elements for growth and development.
While plants can use most colors of the spectrum available in natural sunlight, red and blue are the most valuable for plants. Of all the colors, green has the least impact, and the reason leafy parts of the plant appear green to us is that the color green is being reflected off of them instead of absorbed like the other colors. Blue light encourages leave development, and growth. Red light combined with the blue prompts flowering in plants.
Types of Light
Incandescent light is not effective for plant growth. It produces too much heat and color in the red/orange spectrum. Florescent light has a lot of blue and will produce nice leafy plants, but may not have a good effect on flowering plants. Lights specifically made for indoor plant growth produce the best all-around effects because they are the right temperature, and produce the best levels of blue and red color lighting for plants.
While direct light is good for some plants, others require some shade from direct light. For plants that do need direct light make sure that the intensity is proper for the time of the year, as well as the growth stage of the plant. Young plants, or established plants early in a new year have more tender leaves that will scorch faster than older plants, or plants that have time to adjust to light during summer. As plants grow they develop a better wax coat on their leaves to tolerate higher levels of light.