There are three distinct phases in the production of a flower.
1) induction
2) initiation
3) development

A great number of studies have been carried out on the effects of light on flowering. In the inductive stage in photperiodically-sensitive plants, a substance is produced as a result of the Inductive Photoperiod. This substance is transported to the apex where floral initiation takes place. Initiation marks the change in cell differention and development which lead to floral tissues, and the developmental stage includes that time in which the floral tissues develop into mature flower.

Flowering starts when the Inductive Photoperiod begins, either at the 12/12 switch or when placed into 24-36hrs of dark prior to 12/12.

Hope this helps.
oldmac Reviewed by oldmac on . When is flowering considered started?? Hey all.. I just realised there are a few differing opinions as to when "Day 1" of flowering starts. I've got my own log going and considered it to be from the point I switched to 12/12. I've been reading around and others believe it's from the point the plant changes growth patterns etc. Where do you peeps stand on this? Cheers Rating: 5