By: Scott Eckert, County Extension Agent, Horticulture
Starting your own garden plants is a fun winter project! Many gardeners use fluorescent lights to start young vegetable and flower plants during the spring or to grow certain houseplants all year long.
Traditionally, we have used fixtures with T-12 lamps suspended a few inches above the tops of the plants. However, T-12 lamps are fading away due to newer lamps that are a better choice for indoor gardens. These are known as T-8 and T-5 lamps. The number after the “T” refers to the diameter of the lamp in eighths of an inch. Therefore, a T-12 lamp is 12/8 or 1.5 inches in diameter and are what most people are familiar with. A T-8 is 8/8 or 1 inch in diameter, and a T-5 is 5/8 of an inch in diameter.
So, does a smaller diameter mean less light? Not at all. In fact, the T-5 can be the brightest of the three. Another advantage for these newer lamps is they use less electricity per lumen. Our traditional 48-inch T-12 is rated at 40 watts. However, there are newer styles of T-12’s that are 34 watts. The T-8 is rated at 32 watts and the T-5 at 28 watts.
This sounds too good to be true. Are there draw backs? Maybe so or maybe not. First is cost if you have to replace T-12 fixtures to convert to a T-8 system. However, newer fixtures may be able to handle either T-12’s or T-8’s. Therefore, if you purchased fluorescent fixtures in the last few years, check to see if they are rated for T-8’s before replacing them. Note that lamp costs are comparable between T-12’s and T-8’s. The T-5 lamps are significantly more expensive and cost over twice as much as either a T-12 or T-8.
The question becomes, is it worth it? If you have a T-12 fixture that is rated for T-12’s only and are satisfied with your results, then maybe not. However, if you are investing in new fixtures or have fixtures that can use either T-12’s or T-8’s, then go with the T-8’s. They will use less energy, last longer and provide more light.