Light Intensity

• The intensity of light is a measure of how strong or bright a light is. Plants have adapted to growing in a wide range of light intensities. When plants are grown indoors, they require a light intensity similar to what they would receive in nature. Meeting this need satisfies one of the main requirements plants have for adapting to artificial light.
  
  

Duration of Light

• Most plants grow best when given long hours of bright light, even though this doesn't mimic the seasonal lighting changes that occur in nature. More is not always better, however. In some cases plants are sensitive to the length of the day and will not grow properly unless artificial light follows the same pattern. For most plants, though, day length is not important, as long as they get an unlighted rest period of about eight hours out of every 24.
  
  

Light Color

• The color of the light waves is what controls the quality of the light. Shining light through a prism breaks it down into its different components. Sunlight has a broad spectrum of light waves, starting with blue at one end and ranging to red at the other. In nature, plants are exposed to all these colors of light. But to grow, they need only some of them. The main light color required by foliage is blue light, and the main color needed for plants to flower and fruit is red. Artificial light that can supply these types of light waves will work to grow plants.
  
  

Light Types

• Several types of artificial light are commonly available. One of the most common is incandescent light, supplied by a standard light bulb. Incandescent light is mostly red light, given off at an intensity too low for most plants to benefit from. Standard fluorescent lights, used in many commercial settings as well as other applications, provide blue light almost exclusively. Because these lights are cool to the touch, they can be placed close enough to plants to provide adequate intensity. Fluorescents promote the growth of foliage plants. Grow lights have a mix of light wave colors. All kinds of plants will grow if grow lights are used instead of sunlight.