How do cold frames help botanical gardens care for young plants during winter?

In botanical gardens, cold frames serve as essential structures for protecting young plants during winter. These low, enclosed beds are covered with a removable sash made of glass or plastic, which allows radiant energy from the sun to pass through and warm the soil during the day.1

At night, the cover prevents this heat from escaping, creating a warmer environment than the outside air. This mechanism is particularly useful for "wintering over" young plants that require a cold period to thrive but cannot tolerate freezing temperatures. By providing this controlled environment, cold frames help botanical gardens maintain species that need protection from harsh winter conditions without the need for artificial heating.123