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Floating row cover keeps insects out. Source: rhinowindows.info

One of the most unusual yet effective “pesticides” is floating row cover, also called row cover, garden cover or frost cover. It’s a translucent, extremely lightweight fabric that lets rainwater, air and sunlight through to the plants it covers. It was originally designed to provide frost protection for early plantings and can still be used for that purpose. However, I’ll bet dollars to donuts that more gardeners today use it to protect their crops against insect pests. And here’s how it works.

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These very frustrated potato beetles can smell and see their host plant, but the row cover keeps them away. Source: www.amazon.com.

Loosely cover the row or bed of the susceptible plant with floating row cover (install it on a windless day if possible) and use stakes, bricks or stones to pin it down, otherwise it will quickly blow away. Cover the bottom edge of the fabric with soil all the way around: you don’t want to leave any gaps where insects could enter!

When the plants emerge from the soil beneath the barrier, its usual pest will quickly find them by the smell they give off and will land on the row cover, ready to feed. But it can’t penetrate the barrier! You’ll see the poor bug pacing, turning in circles, examining every fold in the fabric, but there’s nothing it can do. Hungry, it will either fly away to some other garden or simply die, unable to feed itself.

If It Flies or Hops, It Will Be Excluded

A floating cover is very useful against pretty much any flying or jumping insect, including:

  • Aphids;
  • Bean beetles;
  • Beetles;
  • Borers;
  • Cabbage butterflies;
  • Cabbage loopers;
  • Cabbage maggots;
  • Carrot flies;
  • Caterpillars;
  • Corn borers;
  • Cucumber beetles;
  • Cutworms (migratory species);
  • Flea beetles;
  • Grasshoppers;
  • Leafhoppers;
  • Leaf miners;
  • Leek moths;
  • Onion maggots;
  • Potato bugs;
  • Thrips.

A properly installed row cover will even keep slugs and snails away—assuming they weren’t relay present in the soil where the cover was installed—and will keep birds off freshly sown seeds. It will not, however, be of much use in protecting plants from soil-borne, non-selective insects that are found throughout in the garden (wireworms, non-migratory cutworms, etc.), nor against mammals like deer and groundhogs: the latter will just chew holes right through the fabric to get at whatever tasty morsel is underneath.

No Support Necessary

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Here hoops were used to raise the floating row cover off the plants, but that is just a waste of time. The cover is designed to rise with the plants and cause them no harm. Source: www.gardening-guy.com

One precision: unlike a cloche tunnel that needs a structure of some sort (hoops, stakes, etc.) to hold it above the plants it covers, floating row cover is so light it is simply lifted upwards by the plants as they grow, so there is no need for a support structure. That’s why it’s said to be “floating.”

That said, a lot of overly zealous gardeners do put in a support structure of some sort, as if they find floating row covers too easy and prefer to complicate things. That’s fine if you don’t mind the extra work, but it’s something a laidback gardener would avoid.

For Early Season Use Only

The only true downside to floating row cover is that you can really only use it early in the season. In most cases, it has to come off by midsummer. And there are two reasons for that.

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You’ll need to remove the row cover when your vegetables start to bloom. Source: rurification.blogspot.ca

The first is that row cover excludes all insects, even pollinating ones. For vegetables that require pollination, such as squash, cucumbers, peppers, beans and other fruit-bearing ones, you’ll need to remove the cover when the first flowers start to bloom to let the “good guys” in.

The second is that row cover reduces air circulation and that does keep the plants a bit warmer than the surrounding air. That’s rarely a problem early in the season and in fact, is often a blessing when cool nights hit after the garden has been seeded or planted. However, during the heat of summer, in many climates, it just becomes too hot under any kind of fabric, even a light, airy one. When ambient temperatures reach 85? F (30? C), it will be even hotter under the row cover and it’s probably time to consider removing it.

Of course, when the row cover is removed, your plants are then exposed again to their insect pest again, but usually by this time, the first generation of the pest has likely already come and gone. You’ll only be dealing with the second generation (if there is one) and it tends naturally to be much smaller and less harmful than the first one. Better yet, since you deprived the pest of its main source of food at the beginning of the season, the second generation will likely be less numerous than it normally would have been, with usually only scattered pests reaching your plants. Often, the few stragglers that do start to feed on your plants will not be causing enough damage to be worth mentioning … or can simply be controlled by hand-picking.

Think too that your vegetables will have grown considerably by then. They are no longer tender young seedlings very subject to insect damage, but well-developed plants better able to cope with a bit of insect presence.

Crop Rotation Is Mandatory

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You need to practice crop rotation if you want to create an effective insect barrier. Source: www.westcoastseeds.com

For this technique to be effective, you always have to rotate your crops. Otherwise, when the insect digs its way out of the ground in spring after overwintering at the base of last year’s host plant and you plant the same vegetable in the same spot and then plop a row cover overhead, the pest will be trapped inside the insect barrier. Thus, you’ll be supplying it with a fresh and readily available supply of its favorite plant!

However, if you practice crop rotation instead, you’ll be planting the host plant in spot where the plant did not grow the previous year and where the insect pest therefore did not overwinter. As a result, if you install row cover over a crop growing in a different section of the garden, you’ll effectively keep the pest entirely at bay.


Under normal conditions of use, you can expect floating row cover to have a useful life of about 4 years.

No Harmful Insecticides Required

Of course, one main benefit of using row cover is that you won’t have to repeatedly spray potentially harmful and disruptive insecticides, resulting in less work for you and a break for the environment.

Improved results, reduced effort? Floating cover is just about the perfect tool for the laidback gardener!

7 comments on “The Perfect Insect Barrier!

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