G6515 Lighting Indoor Plants | University of Missouri …

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Houseplants are popular indoor decorations. Attractive and constantly changing, they add a softness of line and provide a bit of nature indoors. However, the ideal location of a plant for decoration may not be the ideal spot for plant growth. Lack of adequate light is the most common factor limiting the growth of plants in many areas of the home. Supplementary electric lighting is usually the easiest and least expensive way to provide enough light for plants that do not receive adequate natural light (Figure 1).

Figure 1 Artificial lighting, if properly designed, allows plants to be grown indoors in nearly any setting.

Light provides the energy plants need to make the food required for them to grow and flower. Plants are the only organisms able to use light to produce sugars, starches and other substances needed by them as well as by other living organisms.

Certain colors in light rays are important for proper plant growth. Leaves reflect and derive little energy from many of the yellow and green rays of the visible spectrum. Yet the red and blue parts of the light spectrum are the most important energy sources for plants, and plants require more rays from the red range than from the blue.

Plants growing outdoors, in greenhouses or close to windows are exposed to a natural balance of the blue and red light rays that plants need. Where plants receive little or no natural light, you must provide additional light from artificial sources.

As a single light source for plants, incandescent light bulbs are not particularly good. They are a good source of red rays but a poor source of blue. They produce too much heat for most plants and, if used, must be located some distance from the plants, thus reducing the intensity of the light the plants receive. They are also about one-third as efficient as fluorescent tubes in converting electrical energy to light. Furthermore, a standard incandescent bulb's life is often only about 1,000 hours, whereas a fluorescent tube's life is normally 10,000 hours or more.

Fluorescent tubes provide one of the best artificial light sources available for plants in the home. Other light sources such as sodium-vapor and metal halide lamps may be used but are not as readily available or adaptable for home use.

Fluorescent tubes are made in many sizes and shapes: circular, U-shaped, square or straight. Straight tubes in 2-, 4- or 8-foot lengths are used most frequently.

Many indoor gardeners use cool-white fluorescent tubes. Warm-white fluorescent tubes also seem fairly effective, but fluorescent tubes listed as white or daylight are less desirable for indoor plant growth. Cool-white tubes produce a small amount of red rays in addition to orange, yellow-green and blue rays. However, the red light produced usually is not enough for plants unless windows or other artificial lights produce additional red rays.

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G6515 Lighting Indoor Plants | University of Missouri ...