The Best Way to Cover Tomatoes in Early Spring

Row covers

• Lightweight polyester row covers are suspended over garden rows with wire hoops. Not only do the covers keep frost off the young plants, but they also protect them from the stress of strong winds. The covers trap heat above and below ground, letting you plant tomatoes as much as two weeks before the last frost date, according to the Colorado State University Extension. Polyester row covers are made from a weblike material that lets in light and water from rain or irrigation. The Penn State Extension recommends using spunbonded polyester rather than perforated polyethylene.

Cold frames

• A cold frame is a bottomless box with a removable translucent lid. Open the lids during the day, then close them at dusk to seal in the day's heat and protect the young plants from frost. You can build them from lumber and attach hinged windows, or use hay bales covered with old window sashes. If glass is too expensive, the University of Missouri Extension suggests covering frames with clear polyethylene (4- or 6-mil) or clear fiberglass sheets. CCA pressure-treated lumber is safe for gardens, but do not use wood treated with creosote or pentachlorophenol.

Plastic plant cones

• Double-walled, cone-shaped plant covers protect individual tomato plants. Fill the flexible plastic with water and open the top for ventilation, closing it at dusk to protect from frost. The trapped water absorbs heat during the day and keeps young plants warm at night. These plant covers also offer wind protection. If you set up the covers a week before transplanting your tomatoes, you will get the additional benefit of warmer soil.

Other cloches

• Cloche comes from the French word for "bell" and was first used to describe glass bell jars used in gardens. Today, it refers to any object that protects tender plants. Covering your young tomato plants with plastic bottles, milk jugs, glass jars, metal cans, even laundry baskets will keep away frost. The key is to remove them in the morning, so your tomatoes can get sunlight but not overheat.