How to Use Fluorescent Grow Lights for Hydroponics

Overview

Standard fluorescent grow lights are most frequently used to grow leafy vegetables such as lettuce and spinach, although some modern fluorescents provide the added flexibility to provide adequate performance for just about anything you'd like to grow. Using fluorescent grow lights for hydroponics properly is first a matter of choosing the right type for the right task, then ensuring adequate output, light coverage and mounting position in relation to your plantings.

Step 1

Investigate and decide on the type of fluorescent grow light you'll use. You can use a standard two-bulb, 4-foot-long shop fixture for your grow system, but make sure the bulbs you use say "high output" or "plus." T5 fluorescent grow light fixtures are designed to pack more light into a smaller space. They also have curved reflectors behind each bulb to help direct more of the light down to the plants where it is needed. The downside to these lights is that they're more expensive. Compact fluorescent light (CFL) growing units are similar in performance to T5s, only in a smaller package. CFLs can concentrate the same light output into a smaller package while generating less heat and using less electricity than the equivalent incandescent light. These specialized grow lights are priced similarly to T5s.

Step 2

Determine how much light is needed. There are mathematical methods for calculating light output in the interval of the light spectrum (from 300 to 700 nanometers) that plants and other photosynthesizing organisms can utilize, measured in photosynthetically active radiation (PAR) units. This can get overly complicated for practical home use, so here's a basic rule of thumb: Using two or three of any of the fixtures discussed here for each growing system unit will provide an adequate light field for any kind of vegetative growth you wish to undertake up to a plant height of two or three feet.

Step 3

Mount the fluorescent grow lights so they are at a height within 3 inches of tops of plants. Chain-mounted fixtures are ideal as the mounting height can be adjusted at will. Raise the lights as the plants grow so that the tops never touch the lights, but are within 2 or 3 inches of touching the lights. Fluorescents run coolly enough that the lights won't burn the plants if they're that close (even of they touch the plants), but the light won't reach the lower levels of the plants if the fixtures are too close.

Things You'll Need

  • Full-spectrum fluorescent grow light unit, chain-mounted
  • T5 grow lights (optional)
  • CFL grow lights (optional)

References

  • Jason's Indoor Guide: Fluorescent Grow Lights for Gardening
  • OpenWetware.org: Photosynthetically Active Radiation (PAR) Units (pdf)
Keywords: fluorescent grow lights, fluorescent hydroponic lighting, hydroponic grow lights

About this Author

Lawrence Harris is a consultant, author and web entrepreneur whose 25 years of writing have covered the spectrum from straight news, to technical reports, to features. He has written for the Boca Raton News, Coral Springs Magazine and Wedding and Event Videography Magazine. He attended Florida Atlantic University, majoring in communications.

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