Quote Originally Posted by Opie Yutts
trynagethigh is kind of right about the kind of cfl needed for flowering. Though it's mostly in the correct color range, many people are saying what we want is warm white, or better yet very warm white.

Ultimately we want to look for a more specific color than what people are calling all manner of white. This is subjective and can lead to hibernating plants if you're not careful.

The numbers we are looking for are the Kelvin temperature scale, for measuring color of light, and you should not buy any bulb without checking this first. It's usually on the package. The color of light we want corresponds to peak chlorophyll activity of plants, therefore the most efficient colors for veg and bloom lights are 5500 or 6000 (not between) for vegetative growth, preferably 5500, and 2200 or 2700 (not between) for blooming, preferably 2200. The soft white are usually somewhere above 3000, which are not too good for our purposes. Whether youâ??re buying CFL or HID make sure you look for those numbers.
Technically this is all correct.
However, the color spectrums of CFL's are not that narrow. Almost any CFL will have enough of the correct spectrum to grow good cannabis.
I have seen the greatest success with 'daylight' (5000 - 6500K) bulbs. They have a broader spectrum than other CFL's, and can actually be used in both veg and flower with good results.