Cold Frame

A low, box-like structure with a transparent lid (typically glass or polycarbonate) used to extend the growing season and protect plants from cold, wind, and frost. Cold frames capture solar heat during the day and provide insulation at night. They are used for hardening off seedlings, overwintering tender plants, starting early-season crops, and growing cold-hardy greens through winter. They require ventilation on warm days to prevent overheating.