im still a newbee, and this is only my 2end grow, but im pretty sure that your plants will finish if you have them in a greenhouse and the temp wont drop bellow freezing
my seeds got put in the soil in late april, flowering started mid july and i all ready harvested one, try to look up some danish strains like " royal dane " or " BBQ bwanas blacony queen" i read on some danish grow forums that these strains will flower before 12/12, and its looking like they do