Row cover
In horticulture, row cover (or cloche) is any material used as a protective covering to shield plants, usually vegetables, primarily from the undesirable effects of cold and wind, and also from insect damage.
Material
Commercially available row cover is usually a lightweight synthetic, such as clear plastic (polyethylene) or spunbonded polyester. It is placed directly above rows of crops on a supporting framework—often, on wire hoops to form a low tunnel—and usually left in place for several weeks until crops are well-established.
Floating row cover is extremely lightweight row cover fabric that can be placed directly over plants, without need for a supporting framework, instead being simply anchored to the ground against wind.
Another form of light weight row cover is made from High Density Polyethylene (HDPE) and is a knitted fabric. It is strong and the manufacturer claims a life of 8 years. It is designed with a low shading effect (16%) and allows natural air flow and rain and water penetration. It also protects from light frosts, strong winds and hail. It is used on low tunnels. It comes in a variety of widths and lengths.
A protective tunnel formed with row cover is sometimes called a cloche. More often, a cloche, or bell jar, refers to a covering made of glass or plastic, placed over individual plants to provide similar protection as row cover.