Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

within determine the spectrum of colors emitted by the lamp. Electricity arcs between the two electrodes located at each end of the tube, stimulating the phosphor to emit light energy. The light emission is strongest near the center of the tube and somewhat less at the ends. If rooting just a few cuttings, place them under the center of the fixture for best results.
    Once the fluorescent is turned on, it will take a few seconds for the bulb to warm-up before an arc can be struck through the tube. Fluorescents blacken with age, losing intensity. Replace bulbs when they reach 70 percent of their stated service life listed on the package or label. A flickering light is about to burn out and should be replaced. Life expectancy ranges from 9000 hours (15 months at 18 hours daily operation).

Compact Fluorescent Lamps
    Available since the early 1990s, compact fluorescent lamps (CFL) are finally available in larger wattages. The larger CFLs are having a major impact on small indoor grow shows. CFLs are similar to long-tube fluorescents but boast increased power, smaller size, and an electronic ballast that ensures longevity and precise spectrum rendition. Although not as bright as HIDs they are available in Cool White and Warm White spectrums and generate little heat. Compact fluorescent lamps are perfect for growers with a limited budget and a small space. They run cooler than HIDs and require minimal ventilation.

Fluorescent lamps are great for rooting cuttings. Some people even use them to grow cannabis. Buds that flower under fluorescents lack density and weight.

Light spectrum of Warm White (2700 K) fluorescent bulb

Light spectrum of Daylight (6400 K) fluorescent bulb

Light spectrum of Cool White (4100 K) fluorescent bulb
    When CFLs were first introduced, wattages were too small, and bulbs did not emit enough light to grow cannabis. New large-wattage CFLs are much brighter than smaller, low-wattage CFLs. Several years ago, European companies started selling 55-watt CFLs and Home Depot began to sell a 65-watt CF flood light for $30. Soon afterward 95, 125, and 200-watt CF lamps made in China became available in North America and Europe. The new lamps changed the way growers looked at CFLs. The new CFLs provide enough light to grow cannabis from seed to harvest.
    Compact fluorescent lamps used to grow cannabis are available in two basic styles and shapes. Modular CFLs have independent bulbs and ballasts that can be replaced separately. The bulb is shaped like a long “U” with a two- or four-pin fixture (these lamps are designated “1U”). The 20-inch (50 cm) long “1U” 55-watt, dual-pin base bulbs are common in Europe. Normally, two 55-watt lamps are placed in a reflective hood. Shorter U-shaped bulbs are common in North America, the United Kingdom, Europe, Australia, and New Zealand.
    The second type consists of miniaturized fluorescent tubes packaged with an attached (electronic) ballast. The short lamps consist of several U-shaped tubes (designated 4U, 5U, 6U, etc., for the number of U-shaped tubes) that measure from eight to twelve inches (20-30 cm) not including the two- to four-inch (5-10 cm) attached ballast and threaded base. Smaller wattages fit into household incandescent light bulb sockets. Larger 95, 125, 150, and 200-watt bulbs require a larger mogul socket. Common wattages used for growing cannabis include 55, 60, 65, 85, 95, 120, 125, 150, and 200.

This end view of different sized fluorescent lamps shows their diameters.
    Lighting and specialty stores sell CF lamps, but often charge more than discount warehouse stores. Look for deals at Home Depot and other similar discount stores. Check the Internet, for example, www.liahtsite.net is an outstanding site that also has a retail store locator. Philips is producing some of the higher wattage lamps. Their PL-H bulb is a 4U bulb available in 60, 85, and 120 wattages with Kelvin ratings from 3000 to 4100.
    Beware of manufacturer and reseller web sites making outrageous claims about CFL performance. The most common exaggerated claim is found at the Lights of America site about the 65-watt Florex security light. The package claims the lamp produces 6825 lumens, but an asterisk directs you to the bottom of the box and explains these are “brightness lumens” not “photometric lumens.” A look at their website www.liahtsofamerica.com claims the 65 watt Florex produces 4550 lumens. We tested them and we can agree with 4500 lumens.

Fluorescent lamps