An unheated outdoor enclosure used to extend the growing season or harden off seedlings. It consists of a solid frame built close to the soil with a sloping, transparent lid made of glass or plastic. The structure traps solar heat and blocks wind, creating a microclimate that prevents frost damage without the expense of a full greenhouse.
Heard on the job
We need to move the tomato seedlings out to the cold frame so they can toughen up before transplanting.