Yago,

The problem with those spiraled fluorescent incandescent replacement bulbs is that their phosphors are formulated to mimic the warm light of an incandescent, which makes them very poor in blue light, just like the incandescent bulbs they replace.

Hence they aren't much better than incandescent bulbs for the plants. They do use less electricity and presumably last longer than an incandescent bulb. But in my opinion they are inappropriate as grow lights.

MM

They work just fine as grow lights as long as you get them in a strong enough bulb. 42W would be the smallest I'd suggest, and this size is available from your local HD. Spirals are available in wattages as high as 105W, and in every color imaginable-6500K/Daylight, even.

I have had many orchids and other houseplants in front of a 42W bulb in my growing area. The orchids have spiked, and the houseplants have flowered and grown. The color temperature of the bulb doesn't seem to make a difference, IMO, but I get 6500K whenever possible.

Sam