Home Gardening

Supplement natural light levels artificially
Mississippi Gardens Newspaper and Web Column - December 15, 2003

Proper lighting helps insure that plants kept indoors continue to grow well while they are being protected from freezing conditions outside. Light is so extremely important to plants since it is the source of energy for making plant food. Without adequate light plants become weak and spindly.

Last week's article contained descriptions of light levels that may be available in various locations in the home. Windows and glass doors with east, west, north and southern exposures all yield different sunlight levels at various times of the year. However, houses are usually designed for people and not plants; so what should be done if disastrously low natural light levels are available for your plants?

When natural light levels are insufficient, artificial light can be used to supplement or replace it. Incandescent light bulbs are not good choices for giving plants supplemental light because they do not release enough of the necessary light wavelengths that plants need. They transmit enough red light but not enough blue. They also generate too much heat and must be placed at safe distances from plants that further diminish the light intensity.

A more reasonable and effective choice for artificial lighting is cool white fluorescent bulbs. Although these tubes come in various forms such as circular and U-shaped, most people use straight tubes in 2, 4 or 8- foot lengths. Cool white fluorescent bulbs produce much of the light plants need such as those in the blue wavelength range but are deficient in red wavelengths. Fortunately, there are other special fluorescent tubes that are commonly referred to as "grow lights". One of these special tubes in combination with a cool white fluorescent tube in the same fixture should produce enough balanced light with enough blue and red wavelengths for plant growth.

The intensity of light diminishes with distance from the light source. Plants should therefore be placed with their leaf tips about 6 to 12 inches from the light tubes. Ideally, the light fixture should be adjustable so as to raise it as plants grow. Workshop fluorescent light fixtures are easily hooked to light weight chains with S-hooks for convenient height adjustment.

There are other light sources such as High Intensity Discharge lamps (HID) available for home use that yield more light than any other "grow lamps" and more efficient. However, the extra light quality and efficiency costs more. Look for these light systems that are UL approved. HID lamps are available with light intensities that cover areas from 2 to 100 square feet.

With proper lighting your indoor plants are more assured of improved growth and development offering years of enjoyment and satisfaction. Happy gardening!

These archived columns were written by Kerry Johnson, a hobby gardener, former weekly newspaper columnist and an Area Extension Horticulture Agent for 11 coastal counties in Mississippi.