I'd say it's been flowering for about 2-3 weeks...but that's pretty hard to tell from the picture. As stated before, CFL's don't put out enough light intensity to penetrate into the canopy...which is why you're getting one fairly dense cola, and little side branching. Either, a) buy yourself several more fluorescents and cover the lower branches with a warm light, or b) invest in a small 250-400w HID setup for your next grow. CFL's can produce fairly substantial amounts of bud, but from what I've heard by people who use them exclusively, LST is almost necessary in order to produce a sizable yield.