How do hot caps, cloches, and plastic tunnels protect horticultural crops from cold weather?

Hot caps, cloches, and plastic tunnels are effective tools used in horticulture to protect crops from cold weather by reducing radiational heat loss and creating a warmer microclimate around the plants.12

• Hot caps: These are cones made of translucent paper or plastic placed over individual plants in the spring. They function as miniature greenhouses, trapping solar heat to keep the plants warm.2
• Cloches: Traditionally small glass sashes, these structures are placed over rows of plants to provide a protective barrier that helps maintain higher temperatures.2
• Plastic tunnels: These are typically made of polyethylene and supported by wire hoops spanning the plant rows. They serve the same purpose as cloches by creating a sheltered environment. As the season progresses, these tunnels can be slashed or opened to prevent excessive heat buildup, allowing growers to regulate the internal temperature.2

By acting as physical shields, these methods help mitigate the impact of radiation frost, which occurs when heat escapes from the ground and plants into the clear, calm night sky.13