I live in northern Alberta and planted some 'fem autos' outside a few years back for my first try at growing them as regulars don't start flowering until the middle of Aug and we've had snow and/or killing frost before the end of Aug before.
Most of them came out as male when they started flowering so I ended up with one girl who grew as a regular. I used some tubing we had for a greenhouse and wrapped it in plastic and put a heater inside on a thermostat. For the front of it I used a big sheet to prevent condensation building up when it got cold at night. I also covered it with thick blankets at night to keep the heat in. All went well until one evening the wife plugged an extension cord into the same outdoor plug my heater was on and blew the breaker causing a lot of frost damage to the plant. Still got a pound or more off it and would have cropped in another week so didn't have to spank her like a naughty girl.
I used long pipe cleaners sometimes linked together to pull the heavy colas closer to the centre and keep the branches from snapping off as one did when it was open during the day and wind came up. 5ft tall there. You can't see it but I had a remote temp/rh sensor hanging in the middle of the plant to be able to check temps from the mancave.
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Was keeping the sheet on the front some days when it was staying a few degrees C below freezing all day. 17th of Oct here.
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2 days later.
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2 days after that.
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3 days after the freeze. I had a bamboo stake to support her earlier but she was falling over as the colas got larger so drove a 6' length of rebar 3' into the clay underneath and tied her up to that.
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Grew some real autos the next year and got a couple that came out pretty good and were all done by the middle of September. Five I planted the next year got pollinated by a field of hemp 5 miles down the road so I haven't grown any more outside since.
Trimmed off all the fan leaves in prep to harvest the next day. Got a little over 6oz dry bud off each and about the same in sugar trim. Just under 3ft tall.
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Good luck with yours!