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Row covers are fabric that protects your plants from cold temperatures, too much sun, and insect pests. They screen out Japanese beetles, potato beetles, cabbage worms, leaf miners, carrot flies and most vine borers. Yet, they still transmits the light to your plants without allowing heat build-up.

Water passes through it and is not absorbed. Often referred to as reemay, depending on the thickness it will allow between 30% to 90% of the available sunlight to reach the crops underneath. The heavier the fabric the less light is transmitted. If is reusable and if stored in a dry location where mice can’t make a nest in it, it will last many seasons.

Types of Row Covers

• For frost protection, look for the heavyweight row covers. They let in less light but trap heat, raising the temperature under the cover a few degrees, often enough to make the difference between life and death for tender plants. Don’t use a heavy cover after the weather has warmed or you run the risk of cooking your plants.

  Most row covers are garden fabric made of polypropylene, which not only protects plants from frost damage (down to 28 degrees F) but also allows light through, traps heat in, keeps bugs out, and is an excellent windbreak. It also allows rain and overhead irrigation to reach plants and soil. 
  
  You can also find even thicker fabrics at some garden stores that protect plants from frost down to 24 degrees F. This allows you to insulate strawberries, herbs, perennials, small fruits, and other tender landscape plants all winter long.

• Lightweight row covers (sometimes called summerweight fabric) are the best for insect control, letting in 80 to 90% of the light and not overheating, not blocking rain. However, they’re not enough for frost protection.
  
  Applied early enough, they will keep flea beetles from eating holes in your lettuce. They are great for blocking flying insects such as Japanese beetles, potato bugs, bean beetles, grasshoppers, cucumber beetles, squash vine borer moths, root maggot flies, and cabbage moths.
  
  They are not as effective on slugs, cutworms, or insects that emerge from the soil, so you will have to keep an eye on your plants for damage from them. If you are protecting plants such as cucumbers and squash that need pollinating to produce fruit, be sure to remove the covers once the plants start blossoming to let pollinators in. By that time, the plants were usually large and strong enough to survive insect attacks.

If you have trouble with birds eating newly planted seeds or uprooting your seedlings, a row cover is just the thing to keep them at bay. It can also discourage deer, chipmunks, and rabbits.

If you garden on a windy site, row covers can protect your plants from being flattened by strong gusts.

When starting beets and carrots from seed it is important to keep the seedbed moist at all times. This can be difficult to do, especially in a dry year. We have found that laying row cover over the newly seeded beds helps to keep moisture from evaporating too quickly and prevents the soil from crusting over. The emerging seedlings will lift the cover as they germinate.

We hang old, ripped pieces of row cover over the lettuce beds to give the plants some shade and protection from battering rainstorms. It also helps to keep the lettuce cleaner.

Row covers can be laid on the plants and secured around the edges with soil, pins, rocks, or sandbags. This is called floating since it is not supported in any way. If you have left enough slack, the cover pushes up as the plants grow.

How to Support Row Covers

We support most of our covers on wire hoops. Clipped with clothespins and weighted down on the sides with rocks or bricks, they rarely fly away. Our hoops were free, made from old political signs. In most states, the signs need to be removed 7 to 10 days after the elections, so if the signs on public property are still there after that, they are fair game! The heavy-duty wire is perfect, and you are tidying up the roadsides by removing the signs.

You can even use wire hoops and row covers on raised beds. See photo below (from gardeners.com).

The heavy use of row covers might make our garden look like a laundromat has exploded, but anything that deters bugs without using harmful chemicals and gives the plants a fighting chance is worth doing.