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Grow Room Lighting Equipment

Quick Tips:

For vegetative stage bluish light is most effective (metal halide), and for flowering the red spectrum is the best choice (high pressure sodium). 

High pressure sodium are definitley the prime choice of lighting since they can be used during vegetative or flowering.

There are three major types of lighting systems available right now: incandescent, fluorescent, and high intensity discharge. Incandescent lights are horribly inefficient (especially the screw-in "grow bulb" type) and really not an acceptable option for plant growth. Although they are inexpensive to purchase, their cost of operation makes them the costliest source of light.

Fluorescents:

Until the early 1980's most indoor growers used fluorescent lights to illuminate their garden. These tubes have tremendous advantages over incandescents. They emit about 3 times as much light as an incandescent (given the same wattage), and the light spectrum is one that plants con use more effectively.

However, they do certainly have their limitations. Light is emitted over a large area, so it is not concentrated. Because of this, the lights have to be hung very close to the plants (usually within 2" or so from the grow tips), and constantly moved to accommodate plant growth. This makes garden maintenance rather difficult, even when the lamps are hung on chains.

Fluorescents are, however, very useful in cloning, and starting seedlings. Because in these stages, a plant is not growing vertically very quickly, the disadvantages of moving the lights are reduced. They also put out a more gentle light than the HID lamps, and release less heat. The fact that they produce less heat is very important to those growing in enclosed and not-especially-well ventilated spaces.

If you choose to use fluorescents, it is best to purchase the 'cool white' variety. The ones that are sold as grow lamps (including grow-lux, vitalite, etc.) are much less efficient than a standard fluorescent, and just do not put out enough light to be useful. The slightly different spectrum produced by these lamps does nothing for most plants. Some growers have reported excellent results by using a mixture of cool-white and warm-white lamps in a florescent fixture.

High Intensity Discharge Lamps (HID's)

High intensity discharge lamps are easier to use, and more efficient. Low wattage HIDs are sometimes sold for household outdoor use. Large Wattage lamps are used for lighting streets, parking lots, stadiums and other large areas. They come in two basic flavors:

METAL HALIDES
or MH lamps emit a white light that looks slightly bluish. They are used to light stadiums, convention centers, gymnasiums, and other large areas where a natural looking light is desired.
HIGH PRESSURE SODIUM
or HPS lamps emit a pink or amber light. They are used for lighting parking lots and other areas where the color of the light is not important. HPS units are much more efficient than MH ones, producing more light and less heat per watt of energy consumed. They are often used alone with no detrimental effect on the plants, and will promote faster plant growth than MH lamps during both vegetative growth and flowering. Combinations of bulbs are _NOT_ required, as the HPS lamp does produce all of the light spectrums necessary for healthy growth.

There is a relatively now type of HPS lamp that has become available. It is called the San Agro lamp (Look in _Grower's Edge_ Magazine for more than a few distributors. Basicly the designers of this lamp took a 400w HPS lamp, and added another 30W element to it, However, this new element puts out blue light, to help fill in the parts of the spectrum that a standard HPS is missing. Hydroponics magazine thinks they're terriffic, I can't disagree.

MH lamps are available in 175,200, 400 and 1000 watt sizes. HPS lamps come in 50, 75, 150, 400 and 1000 watt sizes. San Agro comes in 430w only, but it works with a 400w HPS ballast. Each lamp requires its own ballast, which comes with the fixtures that are designed to use these lamps, and are also available separately.

The following chart shows how much light each lamp emits, and the area that it covers adequately: