How Do Grow Lights Work?

Using Grow Lights

In the winter months, individuals who have moved ferns or other plants indoors may notice the plants exhibiting signs they aren't getting enough sunlight. Plants use light to manufacture food through photosynthesis. Even if those plants have direct exposure to a window, they may not receive the 12 to 18 hours of light some plants need. To compensate, home owners can supplement the natural winter sunlight with fluorescent lights or grow lights. However, plants do better under grow lights than fluorescents.

Fluorescent Lights, Grow Lights and LED Lights

Grow lights mimic the sun's rays by producing light at the right temperature for plants to grow. One of the most popular types of indoor grow lights is a high intensity discharge light (HID). These lights are often used in greenhouses and hydroponic gardening. Most plant systems that use indoor lighting require 1,000 watts per 16 to 20 feet of plant area. However, HID lights produce a large amount of heat and are more expensive than compact fluorescent bulbs. For this reason, many home gardeners select fluorescent bulbs instead. However, fluorescent lights don't provide light at the optimal light temperature that plants need for growing and developing new leaves. Fluorescent bulbs work best with plants that prefer indirect light, such as African violets, or plants that are low growing such as lettuce or spinach. LED grow lights have emerged in recent years as an inexpensive, bright and long-lasting alternative to traditional grow lights. LED lamps do not consume much power and do they put out much heat. They can be manufactured to produce light at the specific wavelength that the plant needs to thrive.

Inverse Square Law

All grow lights are affected by the inverse square law, which states the further a plant is from the source of light, the weaker the light becomes and the less effective the light is at nurturing the plant. HID and fluorescent grow lights seek to maximize their output through the use of hoods around the lights. Due to their small size, LEDs may be mounted on movable frames and repositioned around the plants.

Keywords: Indoor gardening, Grow lights, Supplemental lighting, Greenhouse lighting, Hydroponic lightin

About this Author

Tracy Morris has been a freelance writer since 2000. She has published novels and numerous online articles. Her work has appeared in national magazines and newspapers including "Ferrets," "CatFancy," "Lexington Herald Leader" and "The Tulsa World." She holds a Bachelor of Arts in journalism from the University of Arkansas.