This term describes a wide variety of plant covers that let in light and protect plants from frost. The first cloches were made of glass and were unventilated, heavy, and cumbersome. Present-day cloches are made from a range of materials and take a number of shapes. You can buy cloches such as individual plant covers and row covers; or make your own with plastic 4L milk jugs and some creativity. Cloches work like greenhouses by letting in light that warms the soil. The stored heat in the soil is released slowly at night. Use your cloche to harden transplants, and protect tender plants from wind and pests.