Why Use CFL's?
Because not everyone has a big space to grow in and when space and heat are an issue, HID's become less practical as you are faced with either rigging a cooling system which could involve cutting holes in walls, ducting, and more power usage, and of course more $$$. Or, what if you're just growing a couple plants at a time to keep your own stash full (like me), and don't want to go through the trouble of HID lights? CFL's are everywhere, in all shapes and sizes, and are CHEAP. Most need no special fixture, and can be placed much closer. They are a great way to start out growing, keep a small crop going, or use with HID lights. With practice, your CFL grows can rival your neighbor's HID grows.
Types: CFL's come in mainly two flavors; Soft White (color temperature 2700k) and Daylight (color temperature 6500k). For a complete grow, you should use both. Soft white mimics the spectrum of a HPS light, and is best suited for flowering. Daylight's color spectrum is like that of metal halide lights, and is excellent for the vegetative stage. This applies to tubes too; around 6500k for veg, 2700k for flower. There are also tubes labeled plant and aquarium. I haven't seen them in CFL form, but they have no real color temp, so I'm not sure on their efficiency. However, I have used them and it's rather slow growth for the watts.
-Daylight: There is a large difference in vegetative growth when going from soft white to daylight. Therefore, I recommend you use daylight CFL's for vegging, even if you are flowering with a HPS light, because they do not stretch the plants. You don't need much light for good veg growth, especially when using 6500k CFL's. If power savings are a priority, 30w per plant can suffice to grow it to about a foot tall, but more is always better.
-Soft White: Of course, use 2700k soft white for flowering. I have no results to back it up, but I like to use a single daylight bulb while flowering too, just to balance the spectrum. Whether it helps or not, it's more light nonetheless.
-Others: See post #13 and #14 for spectrum charts. Anything between 2700k and 6500k will be less effective, to the point of being almost useless for plant growth. Try and stay away from these. Some 5500k bulbs are labeled daylight, and while they are ok they aren't as good as 6500k.
-Size and Brands: I wouldn't recommend using any CFL under 20w, because it's just too damn small. (Remember, when talking CFL wattage, refer to the actual watts used, not the incandescent equivalent, i.e. 26w CFL = 100w Incan.) Lights of America is a cheap brand. GE and Phillips are big names, and make a more reliable and slightly more powerful product since they have a name to uphold. Oversized CFL's 65w and up work great too, either a self-ballasted screw-in type, or the type that needs a special fixture with the ballast built into it.
Using CFL's: One of the advantages of CFL's is that they screw into any normal light socket. Therefore, mounting options are endless. Take into account the size, shape, and heat given off by CFL's when deciding how to place them.
-Light comes from every square inch of the bulb, and to get the most out of them, try to have every inch facing as much plant matter as possible. More light comes off the side of the long 42w spirals than the front, for example. CFL's are not as intense as HID lights and do not have as great a range nor penetrate as deep, so distance is critical. Imagine an aura surrounding the bulb up to 6 inches away. Everything within this aura will grow, everything outside it needs more light (For those who've played Starcraft, here's a perfect analogy: Pylons are your lights, buildings are your buds.) You don't want your lights more than 4-6 inches away from your plants. With LST, you can put your CFL's literally inside the plant, between branches so that all the light is being used. Try to light all sides, not just the tops.
-Reflecting light is important with CFL's to use every bit of light they give off. Use good reflectors, paint your walls flat bright white, or get mylar.
-Remember, if your CFL is too close it may burn the leaves, so trimming or a fan may be needed (recommended anyway for stronger stems). Bigger bulbs obviously are hotter than smaller bulbs. Fluorescent tubes can touch the plant without burning it, but an average CFL will roast anything it comes in contact with; even 26w CFL's burn. You want to get close, but not too close. Try to stay about 1 inch away. Having a fan blow right through the plant over all the lights helps get them closer. And monitor your plants so they don't grow into the lights. If you're going away for a week, move the lights up in anticipation of your plants' vertical growth.
How many watts or bulbs should you get? How many watts or bulbs should you get? There's no real answer, just the rule that more is better. A good starting point is 100 watts per plant. Any more can usually share the light already there, so maybe 30-50 additional watts each, depending on your situation (remember, look at actual watts used, not incandescent equivalent.) You can tell when you need more light, when parts of the plant are in shade and buds are barely coming in. Those areas need some direct light. Once all bud sites are well lit, you shouldn't be disappointed. You can add as many lights as you can fit, respecting power, heat, and space. But don't leave parts of the plant in the shadows; get another 26w CFL and stick it in that hole.
Edited by SmknVTEC, 01 May 2012 - 04:27 PM.