Cold frame

This allowed seeds to be germinated in the greenhouse and then easily moved to the attached cold frame to be "hardened-off"[2] before final planting outside.

This is parallel to the way that some greenhouses are called "hothouses" to emphasize their higher temperature, achieved either by the solar effects alone or by auxiliary heating via a heater or HVAC system of some kind.

They are most often used for growing seedlings that are later transplanted into open ground, and can also be a permanent home to cold-hardy vegetables grown for autumn and winter harvest.

Cold frames can be used to extend the growing season for many food and ornamental crops, primarily by providing increased warmth in early spring.

Some crops suitable for growing in a cold frame include lettuces, parsley, salad onions, spinach, radishes and turnips etc.