Why use a Grow Light?
Most plants need light to thrive because light is essential for photosynthesis. Without it, plants could not make food. But light can also be too intense, too hot, or last too long for growing healthy plants. In general, more light seems to be better. Plant growth accelerates with abundant light because more of the plant’s leaves have exposure; which means more photosynthesis. Two years ago I left two identical planters in the greenhouse for the winter. One was placed under a greenhouse grow lights and one was not. By spring, the difference was astounding. The plants in the container under the light were nearly 30% larger than those not receiving the additional light. Other than for those few months, the two containers have always been side by side. Years later it’s still evident which container was under the light. The container that did not get the added light is perfectly healthy, just smaller. With many plants, however, winter days are just not long enough. Many plants need 12 hours or more of light per day, some need as many as 18.
Adding grow lights to your greenhouse is an excellent option if you live in the North and don’t get many hours of winter daylight. Grow lights are an excellent option to replace some of the missing rays. Maybe you do not have an ideal southern location on your property for a greenhouse. Use commercial grow lights to supplement the day’s length as well as the quality and intensity of light. If your greenhouse covering does not diffuse sunlight well, you can add lights to fill in shadows for more even growth.
Types of Grow Lights
Not all light is the same. Plants respond differently to different colors of light. Light on either end of the spectrum, blue light or red light, have the greatest impact on photosynthesis. Blue light, referred to as cool light, encourages compact bushy growth. Red light, on the opposite end of the spectrum, triggers a hormone response which creates blooms. Grow lights producing the orange and reddish lights typically produce substantial heat, however, some lights are able to produce powerful led grow light with out the heat.

Grow Lights come in all shapes, sizes and price ranges. As a general rule, inexpensive lights to purchase tend to be the most expensive to operate and the least effective. While price is not necessarily an indicator of performance, many of the efficient hydroponics led grow lights require ballasts as well as specialized fixtures. There are a few basic types of grow lights:
Incandescent Lights, Fluorescent, T-5 Fluorescent, High Intensity Discharge (HID) and LED. These lights run the gambit of performance and price range.
New full-spectrum fluorescent lights provide the red spectrum as well to encourage blooming. Combining the lights in a fixture makes for even, all around growth. The next generation in fluorescent lighting includes the new T-5 lights. These new lights have extremely high output but are energy efficient and long lasting. The T-5 lights triple the light output of normal fluorescent lights without increasing the wattage. Plants absorb a high percentage of T-5 lighting because the fixtures function well very close to plants. High output bulbs require a high output fixture to operate, so the bulbs and normal fluorescent fixtures will not work together.
Many commercial growers use High Intensity Discharge lights because they have extremely high output and cover a wide area. HID lights hang high above plants (hanging height determined by the wattage) so the light works well for large growing areas. Operating HID lights require a ballast to deliver power to the lamp and fixture for the light. Most fixtures have a reflective hood which directs light back towards plants. HID lights emit high heat, so they must be placed away from plants to avoid burning the leaves.