When does flowering begin?

With photo period plants, most people say their in flower after they switch their lights to 12/12. They go through their stretch for a couple of weeks and then you notice button size buds. Thats when their finally in true flower. With autos you will first see pistols, then they do their week or couple week stretch and then show button size buds. Thats when their truly in the first week of flower and they can finish anywhere from 6 to 12 weeks. Depending on genetics, health and grow environment.