Flower whenever you want. But for me, the number of weeks you veg will always equal your final result. For example... a plant simply topped at the fifth node (nothing more done to her but evening her tops out), vegged for 4 weeks will produce 2 zips, veg it another week (5 weeks), it will produce a little over 3 zips, veg it 2 more weeks (6 weeks), it will produce a little over 4 zips. And a plant vegged for 8 weeks will produce 6 or 7 zips! And that is all done using a single 288 (3K) board (11 inches from the canopy), with reds running at just 80 watts at the wall!