I tested this last year.. made a simple 15$ G.H and added seed on 11-12 by 5-13 I had my 1st harvest..
taken in feb 2013
pulled clones for my 2013 fall harvest by 3-20-13
one of them on 4-2-13 carmelisous
by 4-30-13 BK
by 5-13
harvest 3 plants (small but it gave me a great gauge on what to do in 2013-2014 spring grow)
Out "winter" temps get about as low as 25-30 at the coldest.. but a cheap cover kept them alive during the night and in the day I would un cover them to allow full sun..
this year I will be using the same GH + about 12 clones for my spring harvest + fall moms