Late Season Canada Auto Experiment

Last year we built a custom design solar greenhouse in our backyard in Central Alberta. The short grow season here can be challenging, with late frosts and large temperature swings throughout the summer. I remember a few years ago getting over 16" of snow in September. The greenhouse is insulated on 3 sides, with the south side angled roof pitched to the suns altitude giving full light transference from February to November. This grow is to experiment with late season growing in the greenhouse. We also have a temperature & humidity data logger, which we have been using to capture data throughout the summer, and will continue into the winter. Estimating around 12-14 weeks puts the harvest well into November, and we can certainly get loads of snow and temperatures down to -20C, so certainly climate control will be the biggest challenge. We try to gain as much heat passively through the glass, which has proven to be very effective. The main shoulder season/winter challenge is retaining heat overnight and on cloudy days. We have a bunch of thermal mass which I have built with painted cinderblocks filled with concrete and water barrels. Much of this is out of the greenhouse at the moment but will be added back in once the weather starts to cool off. I would not be surprised if we need to add some supplemental heat on a thermostat to prevent freezing overnight, but want to minimize this as much as possible. I did install a 20A GFCI in the greenhouse this year and have a natural gas tee close by, but have not yet figured out the final heat solution for this greenhouse. For this grow I am again using a homemade organic soil mix. We blend our soil in large batches and use it for all our container gardening, including all our peppers, tomatoes, cannabis, melons etc... Basically we combine Compost, Coco Coir, Perlite (~30%), vermiculite, worm castings, blood meal, bone meal, epsom salts, dolomite lime. This batch was mixed a few months ago, and I have since amended it further with some additional compost, bone meal, blood meal and some fish fertilizer which I have added over the past few weeks to help boost beneficial microbe colonies. We are using a 5 gallon fabric pot, currently it is sitting in the middle of the greenhouse, however it will move to up on the upper shelves to maximize sunlight hours and warmth overnight once the temps cool down. Germination for me has worked great this year (100%) by soaking seeds in water for 12 hours and then planting directly into substrate. She popped up after about 72 hours, and has been growing steadily. She started in the garage grow box, along with 2 photoperiods (see other diary), on day 4 I have moved her out to the greenhouse.