I think he heats it when temperatures fall below 32 in the greenhouse. I would think the sun keeps it warm enough during the day that he does not have to heat too often on sunny days. The night temperatures would be a different matter and may have to heat then. Of course, Minneapolis has a good bit of snow and very cold temps. I suspect that he has a good fertilization program, too. I think you will be pleased with the size of the fans and the root systems of each.
