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Rowcovers: Benefits & Uses
One of the most exciting developments in the world of horticulture is the innovative use of high tech fabrics, usually referred to as row covers or floating row covers. These lightweight fabrics provide many benefits, including the following:
Modern row cover fabrics are light and water permeable, so it is not necessary to remove them each day to care for your plants. They greatly improve the quality of vegetables and herbs, especially leaf crops such as lettuce, spinach and other greens, by protecting the leaves from wind and cold. These environmental stresses cause the leaves to form tough exterior tissues, making them less palatable. Plants grown under row covers can have perfect, delicately textured leaves, even when grown when conditions are marginal.
Row covers can also be stretched over metal hoops to create a low tunnel. The advantage of a tunnel design is that you can lift sections of fabric along the side to gain access to the plants beneath for weeding and harvesting.
The level of frost protection provided by row covers is based on the weight of the fabric. The heavier the fabric, the greater the frost protection. Heavier fabrics may allow less light and water to penetrate, so you must judge which you need most, the frost protection or the light transmission and permeability. The lightest fabric produced is ½oz. fabric, which means that one square yard of the fabric weighs ½oz. One can expect to obtain a 2°-4° F temperature advantage beneath fabric of this weight. 85% of the ambient light penetrates ½oz. fabric. Use of ½ oz. Fabric can elevate seed germination to 90-95% compared with 60-65% germination using straw as mulch.
In contrast, 1.5 oz row cover fabric provides up to 8° F protection from the outside air, but only allows 70% light penetration.