Controlled freezing--methods
pots in late fall from nursery to greenhouse, 40 °F (4 °C)
uniformly frozen 2 days at 28 °F (-2 °C) in freezers
temperatures dropped 4 °F (2 °C) per hour (similar to natural events)
after freezing back to 40 °F, then to 60 °F in 2-4 wks