Grow Lights

How To Set up and Use a Fluorescent Grow Light

How to set up a fluorescent grow light to create a small indoor garden or indoor propagation area.

Basic Facts

Fluorescent grow lights have come on leaps and bounds in recent years although the general principle remains the same. The old style T12 fixtures have been largely superseded by more efficient T5s which produce more than twice the amount of light as their predecessors. T5 lamps are available in high-output 'HO' and very-high-output 'VHO' models and in two sizes - 2ft or 4ft.

Solar Wind T5 (High Output) Fluorescent Grow Light (8 x 54 watts)

  • Lamp fixtures holding 2, 4, or 8 lamps are most common.
  • HO lamps generate 5000 lumens of light, using 54 watts each.
  • VHO lamp generate 7200 lumens of light, using 95 watts each.

Purchasing Tips

Fluorescent strip grow lights generally illuminate the same area that the fixture itself takes up. So, if your fixture measures 4ft by 2ft, then it will evenly illuminate that area of your garden.

  • Ask whether your fixture runs HO or VHO lamps. They are not cross-compatible so this is really important!
  • Be sure to add up those watts! For instance, an 8 lamp VHO fixture will use 760 watts of power-not an inconsiderable amount, especially when illuminating vegetative plants for 15 - 18 hours a day.
  • Check whether lamps are included in the purchase price or if it's "fixture only."
  • Specify the color of lamp you want. Lamps are typically available in cool blue (6.5K) for vegetative growth or bloom (3K). The vegetative lamps are typically used for propagation and mother / donor plants. Bloom lamps are used for providing additional side lighting mature, flowering and fruiting plants. You can mix and match lamps in the same fixture, so long as they are all correctly rated (HO or VHO.)
  • You don't need a ballast. T5 Fluorescent grow light fixtures come with a built in electronic ballast.
  • Don't forget to specify whether you want to run the fixture on a 120v or 240v power supply.
  • VHO lamps generate more heat than HO. It's worth considering the extra investment in an air-cooled fixture. These units have built-in fans and self-cool by passing air over the lamps.

How to Use a T5 Fluorescent Grow Light

T5 fluorescent grow lights should be place directly above your plants. They can penetrate up to about 20 inches and are best suited for starting seedlings or growing leafy greens.

Quality fixtures come with built-in hangers. Make sure the grow light is hung straight and level, ideally with purpose-built hangers to make raising and lowering the fixture easier as the plants develop or you replace crops.

When raising cuttings and seedlings in propagators, position HO and VHO grow lights a good 6-8 inches above the propagator lid and check the actual temperature inside the propagator with a Min/Max thermometer's remote probe to insure it's not heating up too much. Ideal temperature for propagation is in the mid to high 70s.

Growers should replace their lamps after 10,000 hours of use even if they still appear to be working fine (they may still look good to the naked eye but your plants are receiving significantly less energy and more heat!) If using lamps to drive an 18/6 (long day) cycle, this equates to around 18 months of use.

T5 Fluorescent Light used to illuminate two full-sized propagators jam-packed with tomato seedlings!