Although individual plants need different amounts of light to grow efficiently, a lack of quality light may produce plants with elongated stems and deformities because they may stretch toward the nearest light source. Fruit-bearing plants may not set fruit. When adequate outdoor light is not available, artificial grow lights may supplement plants' need for light.
Grow lights are available in three common types, and each one has its benefits and drawbacks. Fluorescent grow lights are small and affordable, and they do not generate excessive heat in the plant area. Unfortunately, they do not produce a high level of intense light, which some plants require for vigorous growth. Low-growing, leafy plants, such as lettuce and spinach, will benefit from fluorescent lighting, and you may increase the illumination factor by adding reflectors that direct extra light back onto the surface of the plants.
Grow lights that include high-pressure sodium (HPS) bulbs are more efficient that fluorescent lights, and the bulbs last longer. However, HPS grow lights also generate heat and they are more expensive. When using HPS grow lights, the grower should arrange for adequate ventilation to avoid excessively high temperatures in the growing area.
The third common type of grow light provides a wide spectrum of artificial light that closely resembles the natural light from the sun. Metal halide grow lights work well for growing vegetables that need high levels of high-intensity light every day. Leafy plants fare well with metal halide lighting, but flowering plants may not produce an abundance of blooms. You may combine two or more types of grow lights to increase light spectrum output.
Determine Lighting Needs
The type of plant you're growing will determine your grow light needs. On average, a plant needs approximately 18 hours of light and six hours of darkness. However, seedlings may benefit from constant light until they develop their first true set of leaves. Placing the grow light closer to the plants will increase the intensity of the light.
Before purchasing grow lights, study the wattage output of each unit. The higher the light wattage, the larger your grow area will be. For instance, a 100-watt bulb will illuminate only a 2-foot square area, but a 1,000-watt bulb will sufficiently light a 6-foot square growing space.
Take precautions when setting up your grow light area to ensure that the electrical cords and bulbs do not encounter water. Accidentally spraying a hot grow light when misting your plants could result in the bulb cracking.