6 Building Effective Row Covers For Pest Exclusion Without Chemicals
Protect your crops without chemicals. Our guide details 6 ways to build effective row covers, creating a physical barrier against common garden pests.
You walk out to your garden one morning to find your broccoli seedlings have vanished, leaving only tiny, chewed-off stems. Or maybe you see your beautiful squash plants suddenly wilt, the base of the stem turned to mush by a hidden pest. This is the moment every gardener dreads, but it doesn’t have to end with reaching for a chemical spray. Effective row covers offer a physical barrier, creating a pest-free zone where your plants can thrive without interference.
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Selecting Fabric: Agribon vs. Insect Netting
The first decision you’ll make is the most critical, and it’s not just about stopping bugs. Your choice of fabric dictates the microclimate you create for your plants. The two main players are spun-bond fabric, like Agribon, and dedicated insect netting. They serve very different purposes.
Agribon is a lightweight, non-woven material that lets in light, air, and water. It comes in different weights, often designated by a number like AG-15 or AG-30. The lighter weights (AG-15, AG-19) are excellent for general pest exclusion in spring and fall because they also provide a few degrees of frost protection. The downside? They trap heat. Using even a lightweight Agribon on a hot summer day can cook sensitive greens.
Insect netting, on the other hand, is a woven mesh designed for one thing: maximum airflow while blocking pests. It offers virtually no frost protection and traps almost no heat, making it the superior choice for summer crops. The key here is mesh size. A larger mesh will stop cabbage moths but let tiny flea beetles through. A very fine mesh stops everything, but can reduce light transmission slightly and costs more.
Your choice depends on your primary goal. If you need a three-season tool for both frost and common pests like cabbage moths, a lightweight Agribon is a versatile investment. If your main enemy is a summer pest like the squash vine borer or flea beetles in the heat, investing in high-quality insect netting is the better long-term strategy.
Constructing PVC Hoops for a Flexible Frame
A row cover is useless without a frame to support it off the plants. PVC pipe is the standard for a reason: it’s inexpensive, widely available, and simple to bend into durable hoops. You don’t need a complicated design.
For most garden beds (3 to 4 feet wide), 1/2-inch or 3/4-inch Schedule 40 PVC is perfect. A 10-foot length of pipe will create a nice arch with plenty of headroom for maturing crops like kale or broccoli. The secret to a sturdy structure is how you anchor it. Cut 18-to-24-inch pieces of rebar and hammer them about halfway into the ground on either side of your bed. You can then simply slide the ends of the PVC pipe over the rebar stakes.
Space your hoops every 4 to 5 feet along the length of the bed. If you live in a windy area or expect late-season snow, place them closer together for added strength. This rebar-and-PVC system is strong enough to handle wind and light snow, but flexible enough to be moved easily from one bed to another as your crop rotation dictates.
Creating Low Tunnels for Brassica Protection
Brassicas—cabbage, broccoli, kale, cauliflower—are magnets for pests. Flea beetles pepper seedlings with holes, and cabbage moths lay eggs that hatch into voracious caterpillars. A low tunnel is the definitive, non-chemical solution.
The goal is to create a sealed environment from day one. Cover your brassicas the same day you plant them. If you wait until you see the first white moth fluttering by, it’s already too late. She has likely laid eggs, and you will have simply trapped the caterpillars inside a fabric-covered buffet.
Drape your chosen fabric over the PVC hoops, making sure you have at least a foot of extra material on all sides. You need this slack to properly seal the edges. The tunnel doesn’t need to be tall; just high enough to accommodate the full-grown plant. A lower profile is more stable in the wind and uses less material.
Securing Edges with Soil for a Complete Seal
The most sophisticated row cover is worthless if a pest can just crawl underneath it. The seal along the ground is non-negotiable, and the best tool for the job is often just the soil from your path.
After draping the fabric over your hoops, leave the excess material flat on the ground. Use a shovel or a hoe to pile soil all along the perimeter, directly onto the fabric. This creates a continuous, weighted seal that even the most determined crawling pest can’t breach. It’s cheap, effective, and conforms perfectly to uneven ground.
While options like sandbags or landscape staples exist, they have drawbacks. Sandbags are effective but bulky to store and move. Staples can be ripped out by strong winds, tearing your fabric and creating gaps. Soil is the gold standard for a complete seal. Just be sure to leave enough slack in the cover so that weighing down the edges doesn’t pull the fabric taut against your plants.
Hand-Pollinating Squash Under Row Covers
Row covers are a game-changer for protecting squash, zucchini, and cucumbers from squash vine borers and cucumber beetles. But there’s a major tradeoff: if the pests can’t get in, neither can the pollinators. To get fruit, you have to become the bee.
Hand-pollination is simple once you learn to identify the flowers. Male flowers have a long, straight stem with a pollen-covered anther inside. Female flowers have a tiny, immature fruit at their base, right behind the blossom. The key is to pollinate in the morning when the flowers are fresh and open.
Gently pick a male flower and peel away the petals to expose the anther. Find an open female flower and carefully brush the pollen from the male anther onto the stigma in the center of the female blossom. That’s it. You’ve done the bee’s job. Be sure to seal the row cover back up immediately afterward. It’s a daily chore during peak season, but it’s the only way to guarantee a harvest while keeping the borers out.
Using Clothespins to Seal Ends and Openings
While soil secures the long sides of your tunnel, the ends can be awkward to seal. This is where pests often find their way in. The simplest solution is also the cheapest: clothespins or small spring clamps.
Gather the excess fabric at the end of the tunnel, bunching it together tightly as if you were closing a bag. Use several clothespins to clamp the bunched material shut. This creates a surprisingly effective seal that is also incredibly easy to open when you need to access the bed for weeding or harvesting.
This technique is also invaluable for managing the cover itself. If you need to work in the bed for a while, you don’t have to unbury the entire side. Simply unbury a 5- or 6-foot section, roll the fabric up the hoops, and use a few clothespins to hold it in place. This creates a temporary doorway that is quick to open and even quicker to close and re-seal.
Reinforcing Seams for Multi-Season Durability
Row cover fabric is surprisingly strong, but it isn’t indestructible. Over time, wind, sun, and friction will create weak spots, especially along seams and at contact points with the hoops. A little preventative maintenance can dramatically extend the life of your cover.
Before its first use, consider reinforcing the main seams with a UV-resistant tape, like greenhouse repair tape. This small step prevents the tiny tears that eventually grow into crop-exposing rips. It’s far easier to reinforce a new cover than it is to patch a hole in the middle of the season.
Pay attention to where the fabric rests on the top of the PVC hoops. This high-friction point is prone to wear. For a deluxe setup, you can slice a pool noodle lengthwise and slip it over the top of each hoop. This creates a smooth, cushioned surface that protects the fabric from abrasion, helping you get several seasons of use out of a single cover.
Timing Removal for Harvest and End of Season
A row cover is not a permanent structure. Knowing when to remove it is just as important as setting it up correctly. The timing depends entirely on the crop you’re protecting and the pest you’re fighting.
For a crop like broccoli, the main threat is the cabbage moth, which is most active in the spring and early summer. Once the broccoli heads are well-formed and pest pressure declines, you can often remove the cover to improve airflow. For summer squash, however, the squash vine borer is a threat for the entire life of the plant, so the cover must stay on until your final harvest. You have to learn the lifecycle of your local pests.
At the end of the season, take your covers down promptly. Brush off all the soil and debris, and if they’re particularly dirty, give them a gentle rinse with a hose. The most important step is to ensure they are completely dry before folding and storing them. Storing a damp cover invites mold and rot, which will degrade the fabric and force you to buy a new one next spring. Proper care is key to making this a sustainable, multi-year tool.
Building an effective row cover system is about more than just throwing a sheet over some plants. It’s a thoughtful process of selecting the right material, building a solid frame, and managing it actively. It’s a small investment of time that pays off with a clean, abundant, and chemical-free harvest.
