Garden with Grow Lights

First, decide what you’re going to grow, and where you’ll place your lights. Natural sunlight has the colors of the rainbow: blue, red, violet, and yellow. Plants need the full spectrum, but use primarily red and blue. While you can use ordinary fluorescents to supplement any daylight that comes in your windows, specialty lights can allow you to grow plants in dark spots that receive little or no light at all.

Traditional fluorescent lights, like those used in shop light fixtures, are the most economical. They’re a good choice if you only need to supplement natural light. These bulbs come in cool, warm, or full-spectrum.

Full-spectrum fluorescents are recommended for seedlings, because they don’t give off a lot of heat that could damage tender foliage. Position them about 2-4″ above the seedlings, and raise them as the plants get taller. They’re also a good choice if your fixtures will be in or around living areas, because full-spectrum light is similar to natural light and won’t distort colors of your plants.

High intensity discharge lights (HDI) are the brightest grow lights and about twice as efficient as fluorescents. They must be used in special fixtures with ballasts.

There are two kinds of HDI lights: metal halide, or MH, and high-pressure sodium, also known as HPS.

MH lights are most intense on the blue end of the spectrum and promote foliage/vegetation growth. Because the lamps don’t distort colors, they can be used in living areas, like full-spectrum fluorescents. Use them to start your seedlings, and change to HPS lights when you want to promote flowering.

HPS bulbs are stronger at the red/orange end of the spectrum, so they’re better for flowering plants. It’s a good idea to combine them with MH lightning or with natural daylight, so your plants won’t become long and leggy. Use these bulbs away from living areas, since their illumination distorts colors.

Note: MH bulbs and HPS bulbs need different kinds of fixtures. If you want both types of light, you’ll need multiple fixtures or a special conversion bulb that allows you to change bulbs without changing ballasts. Always use caution when setting up any kind of lighting or wiring system to avoid injury or property damage.