Hi,

I experimented with a winter grow in a greenhouse this past winter. I am not in as cold of an area as you are in the nights were in the 30s and 40sF days 50s-60s. I used a passive system to keep them warm, water filled containers areound the pots 7 and 15 gallon buckets. I used Swiss Miss seeds since they are suppose to be able to handle colder and shorter seasons. I also took 3liter pop bottles cut off their tops and covered the seedlings with them. I planted them towards the end of Nov. Anyway they grew so slow it was crazy after 4 months they were not even a foot tall. I do not know if it was the cold or the fact that the days were so short that caused the slow growth but suspect it was a combination of the two. I think you would need to add both aditional heat and light source for it to work and if you are going to go through that much trouble then you might as well grow inside. Hope this helps.