T5 Fluorescent

Definition - What does T5 Fluorescent mean?

The T5 fluorescent bulb is similar to other types of fluorescents, and has been around since the 1950s. Two new versions debuted in the 1990s, including a high-efficiency model and a high-output model. All are well-suited for use in indoor and hydroponic gardening set-ups.

A wide range of fluorescent bulbs can be used as grow lights for indoor/hydroponic systems, but the T5 fluorescent bulb is perhaps the most common. They are also used in starting plants indoors for transplantation outdoors after the danger of frost has passed.

MaximumYield explains T5 Fluorescent

A T5 fluorescent bulb is 5/8th of an inch in diameter, making it smaller than some other options out there. Most fixtures that use T5 bulbs cannot accept T8 or T12 bulbs, and vice versa, although there are some fixtures available that can be modified to accept multiple types of fluorescent bulbs depending on the grower’s needs.

However, these bulbs manage to put off more heat, and tend to provide other advantages not found with larger (or smaller) fluorescent lights. For example, in indoor growing experiments for transplantation to the outdoors, users with T5 bulbs found that hardening off the plants was simpler.

Using T5 bulbs also resulted in darker green plants, whereas the use of T8 bulbs required greater effort in hardening before moving to direct sunlight and lighter green plants. With that being said, the greater heat output of the T5 fluorescent bulb requires that it be kept farther from the plants or more frequent adjustments to be made in order to prevent heat damage if the leaves come into contact with the bulbs.

It is also important to understand the light emission range of different T5 fluorescent bulbs. For instance, bulbs with a 3000K (Kelvin) rating produce more light in the red spectrum, helping to encourage flowering. Bulbs with a 6500K rating provide a full-spectrum of light and are ideal for overall growth.

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