Fluorescent Grow Lights

Fluorescent grow lights have seen significant improvements over the last few years. New bulbs produce more and stronger light, and last longer. Most gardeners utilize fluorescent grow lights to grow cuttings, small vegetative plants, and some even use them to flower certain crops. Fluorescent grow lights are now available in many different spectrums, some close to natural sunlight.

Fluorescent grow lights work very well with cuttings because they generate cool diffused light in the proper spectrum to promote healthy root growth. Fluorescent grow lights produce much less light compared to High Intensity Discharge (HID) lights so they must be kept very close to plants (1-3 inches) to get the best results. This isn’t a problem because the lights themselves do not produce very much heat. Leaves may actually touch the lights without being burnt. It’s not recommended to use fluorescent grow lights together with HID grow lights. Since fluorescent grow lights need to be kept close to plants, the fixtures will shade them from the HID grow lights.

Fluorescent grow lights come in many sizes and wattages, and some may require specific ballasts to operate them. Many fixtures come with the ballast built in. The most common bulbs used for growing range from 15 inches to 4 feet in length. Bulbs are available in a wide variety of wattages as well, some as low as 50 watts. Circular fluorescent grow lights are also available, but very rarely used by gardeners.

Fluorescent grow lights are classified by diameter and come in the sizes T12 (1.5”), T8 (1”), T5 (.625”), and CFL (Compact Fluorescent lights). T12 fluorescent grow lights run on magnetic ballasts, while T8 and T5 run on electronic ballasts which run cooler and don’t flicker. The average lumen output of a 40 watt T12 fluorescent grow light is 2800 lumens, about 68 lumens per watt. A 32 watt T8 fluorescent grow light yields 100 lumens per watt, or 3200 lumens. A 54 watt T5 fluorescent grow light yields an average of 5000 lumens, or 92 per watt. Many gardeners who use fluorescent grow lights prefer T5 lights because of their high output.