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

are great for rooting cuttings. Some people even use them to grow cannabis. Buds that flower under fluorescents lack density and weight.
    Furthermore, manufacturers commonly compare the output of CFLs with incandescent lamps. But the comparison is misleading. They claim the 65 watt CFL is equivalent to a 500 watt incandescent. A 65 watt CFL produces the same number of lumens as a 500 watt incandescent bulb. Given this information many people assume that a 65 watt lamp produces as much light as all 500 watt bulbs. Not true.
    Cool White CFLs have a kelvin (K) temperature of 4100, with more blue in the spectrum, which lessens internodal branching space in plants. Cool White CFLs are perfect to grow short, stout seedling and vegetative plants. Warm White CFLs (2700 K) have more red in the spectrum and can be used alone but are best used in conjunction with Cool White lamps to avoid internodal stretching during flowering. A 95- to 120- watt lamp will illuminate a space of about two square feet (60 cm2).

The arc tube of a fluorescent lamp is long, emitting light along its entire length.
    Light from CFLs fades fast and must be placed close to the plants. The bulb produces very little heat and can be mounted about two inches (5 cm) away from foliage to achieve the best results.
    Short U-shaped bulbs are most efficient when vertically oriented. When mounted horizontally under a reflective hood, much light is reflected back and forth between the bulb’s outer envelope and the hood, which markedly lowers efficiency. Heat also builds up from the ballast. Both conditions lessen efficiency.
    Save electricity in the grow house and replace incandescent bulbs with compact fluorescents. Compact fluorescents use about 75 percent less energy than incandescent lamps, and emit 90 percent less heat for the same amount of light. If you replace ten 100-watt incandescent bulbs, you will save 750 watts of electricity!
Construction and Operation
    Compact fluorescent lamps create light by passing electricity through gaseous vapor under low pressure. Compact fluorescent bulbs are coated inside with tri-phosphor which further expands light emission. CFLs must warm up about five minutes so the chemicals become stable before they come to full brightness. Like all fluorescents, CFLs require an appropriate fixture containing a small electronic ballast to regulate electricity and household electrical current. Ballasts are either attached to the lamp (self-ballasted) or integrated into the reflective hood. Smaller self-ballasted lamps screw into a household incandescent bulb socket. Larger bulbs screw into a mogul socket. Each 1-U bulb is hooked to sockets with bi-pin connectors.
    Compact fluorescent lamps will normally last 10-20,000 hours (18-36 months at 18 hours daily use). The life of a CF ballast is from 50,000 to 60,000 hours (seven to nine years at 18 hours daily use). Lamps with attached ballast burn out three to six times faster than the ballast. When the lamp’s life is over, the lamp and the attached ballast are both thrown away, which means you are throwing away a perfectly good ballast! My preference is to use the long CFLs that are not attached to a ballast.
    Compact fluorescent lamps can also be used to supplement the reddish-yellow spectrum from HP sodium lamps. However, the outer case covering the attached ballast is susceptible to deterioration from UV light. When used in conjunction with other HID lamps that produce UV rays, the ballast case deteriorates more quickly. Attached ballasts are not designed for humid grow room applications. Couple this weakness to humidity with a bit of UV light, and bulbs burn out more quickly.
    The end of ballast life is signaled when it stops. When the ballast burns out, remove and replace it.
    Although CFLs are not considered hazardous waste, they still contain a little mercury and should be disposed of properly to avoid contaminating the environment. Place CFL bulbs in a sealed plastic bag and dispose the same way you do batteries, oil-based paint, motor oil, etc. at your local Household Hazardous Waste (HHW) Collection Site.

Other Lamps
    Several other lamps deserve a mention, however, they grow marijuana poorly. Incandescent lamps are inefficient, tungsten halogen lamps are bright but inefficient, and low-pressure sodium lamps are efficient but have a limited spectrum.
Incandescent Lamps
    Incandescent lamps were invented by Thomas Edison. Light is produced by sending electricity through the