Compact Fluorescents (or CF's) are fluorescent lights that can be plugged into a regular incandescent (normal light bulb) fixture.
They are advertised as 'Energy Saving Light bulbs'. Dont confuse their advertised wattage and actual wattage! The advertised wattage (usually in LARGE letters) will say something like 100w. Usually hidden is the actual wattage (say 10w-30w). This rating indicates the CF emits as much light as a 100w incandescent bulb, but uses only 10w-30w.
The 10-30w bulbs will work in your regular lamp or light fitting. The 31-50w bulbs (preferred for growing) are made for outdoors, and require an outdoor light fitting.
Placing Compact Fluorescents
Fluorescent lights do not have the penetrating power of HID lights, so they must be placed very close to the plants, either horizontally or vertically, preferably several CFs to illuminate both sides of the plant(s).
The CF should be mounted about 5cm away from the plant. Too far and they'll stretch, too close and theyll burn! Yes, plants will suffer burnt tips if placed too close.
A good homemade reflector (highly recommended with low power floros) can be made from aluminum. Put a hole through the bottom big enough to get your CF through.
You can take a plant through its entire cycle using CF's but I would strongly, advise flowering with an HID, even if it's only 250w. This will vastly boost potency and yield.
There are only three reasons to use CF's for an entire cycle: 1. an extremely tight budget or, 2. no space, or 3. HIDs are too hot for your grow.
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