I have heard the hill side an plastic on the sides kinda work if its been in flower for about a month or so before the days start getting longer in the spring. especialy if its been on a long daylight cycle before going outside.
Its feasable i think , but i would flower em as long as i could before they go out , or use pots an bring em in to keep the 12/12 going.
But i have never tried it , since no one else has answered yet i figured i tell you what i think