How to Make DIY Hoop Tunnels to Protect Your Garden from Frost, Heat, and Pests

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If you’re like us and you want to get serious about growing more food at home, setting up a system for floating row cover is a must. Row cover is a low-stress way to protect vulnerable plants from both pests and damage from weather extremes. That makes it an invaluable tool for reducing losses, extending your season, and cutting down on your work load in the garden.

Most market farmers use row cover of some kind, whether that’s a high tunnel or low tunnels for single rows. But row cover isn’t just for the pros. Installing hoop tunnels is a super easy DIY project for a little backyard garden, and it’s also not crazy expensive. You can buy low-tunnel kits if you’d rather not DIY, but I hear the cheap kits are poor quality. And the not-cheap kits are…REALLY not cheap. DIYing your low tunnels is the way to go, if you ask me.

The cool thing about a low tunnel system is its versatility. Once you’ve got your hoops installed in the garden, they’ll work for multiple types of row cover. You can use them to hang insect netting as a passive way to keep pests away from your plants, along with frost cover and shade cloth to prevent damage and yield losses during unexpected weather events.

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Supplies Needed for Hoop Tunnels

Growers use a handful of different materials to construct tunnels for row cover. Most of the pros are using metal hoops, since they’re the most durable. You can make your own metal hoops with galvanized electrical conduit, but you’ll need a greenhouse hoop bender to shape them. This gadget will cost you a pretty penny. It really isn’t worth it, for a backyard gardener who’ll probably only use it once or twice to bend hoops.  

Our go-to way to install hoop tunnels is the rebar and PVC method. PVC is cheaper than metal conduit, and you don’t need a special tool to bend it. 3/4 PVC pipe slides neatly over standard #4 rebar stakes, which hold the PVC hoops firmly in place. This works well for individual garden beds in the 4 foot wide range, as well as shallower raised beds.

To make a PVC hoop tunnel, you’ll need:

-3/4 PVC pipe for the hoops, cut to the proper lengths.

You can use either standard plumbing PVC pipe or Schedule 40 PVC electrical conduit. The Schedule 40 is a few dollars more per section but will hold up to UV light for longer. You’ll need enough pieces to space the hoops about 3 feet apart along the length of the bed to provide good support for row cover.

How long they need to be depends on the width of your beds. For my approximately 4’ x 12’ garden beds, I need four 8.5’ lengths of PVC. Err on cutting your PVC hoops a little too long to start, since it’s easy to trim off a few more inches if needed.

-2 pieces of 1’ or 2’ standard rebar for each hoop you’ll install.

You can find rebar in the concrete and masonry section at hardware stores. The 1’ rebar pieces are cheaper and easier to move around, if you decide you want to pull your stakes up and relocate your hoop tunnel. However, they have an annoying habit of popping out when you try to remove a hoop. Those 2’ pieces ain’t budging, once you pound them three-quarters of the way into the ground. They’re great if you want to outfit your whole garden with permanent hoop supports.

-PVC cutters, if your PVC isn’t pre-cut.

-A sturdy rubber mallet.

This makes it easier to pound in the stakes, since regular hammers tend to slip off the rebar.

Installing the Hoops

Before pounding in the rebar stakes, lay them out on each side of the garden bed where your hoops will be to make sure they’re even. Mine are never perfectly lined up, but I’m more about function than perfection. Aim to pound the rebar stakes deep enough that only about 3 or 4 inches or so remain above-ground. If they’re not deep enough, it’ll be harder to get the hoops on.

Once your stakes are in, all you need to do is slide the ends of each PVC hoop onto opposite stakes. This job is easier if you have a helper.

Tip: PVC can be harder to bend on a chilly evening. It’ll be a lot more flexible, if you let it lay in the sun for a few hours on a warm afternoon before installing.

Hoop Tunnels for Deep Raised Beds or Traditional Rows

Deep Raised Beds: Rebar stakes won’t work so well for securing PVC hoops, if your raised beds have higher walls. Your best bet is to use pipe strap clamps such as these instead of rebar. You’ll need a drill, a nut driver, and some screws to fasten them to your raised beds’ walls, but it’s still a pretty simple DIY.  

Traditional Rows: If you grow in a traditional row layout instead of individual garden beds, you might need smaller tunnels for covering single rows of veggies. 3/4 PVC isn’t flexible enough to bend easily at smaller angles. Instead, you can use some heavy gauge wire (such as 12 gauge) to make smaller hoops. No rebar needed; just make the hoops tall enough to push the wire down into the soil a good ways.

Securing Row Cover

Whichever type(s) or row cover you’ll be using, you’ll need to secure it in place on the hoops. Inexpensive greenhouse clips are perfect for securing row cover to PVC. You’ll also need to weight it down along the ground, as well. This way, the wind (or unwanted insects) can’t get underneath it. Use T-posts, heavy boards, bricks, or whatever you have available to weigh down the edges.

Tip: When purchasing row cover, make sure it’s wide enough you’ll have plenty of overhang on either side of the hoop tunnel. It’ll need to be quite a bit wider than the width of your garden bed. For my 4′ beds, I need row cover that’s at least 10 feet in width to secure it properly.

One exception: shade cloth doesn’t always need to cover the whole tunnel, depending on the angle of the sun. Mine (below) is positioned so that it shades the bed during the hottest part of the day and allows in some direct sun in the morning and evening.

Types of Row Cover and How to Use Them

Here are three types of row cover that’ll really level up production in your garden:

Insect Netting

Sadly, I’ve had more than one local tell me they’ve about given up on growing cabbage, broccoli, and other brassica crops around here, since the caterpillars just destroy them every year. That’s understandable. For an organic gardener, it’s HARD to stay on top of hand-picking cabbage worms and applying Bt or Spinosad after every rain shower.

The (almost) foolproof solution to this problem is insect netting. Most destructive caterpillar pests end up on your plants via a moth or butterfly looking for a nice spot to lay her eggs. Netting creates an effective barrier to prevent these pests from reaching your plants in the first place. It’s the ultimate way to slash your caterpillar problems by 90+ percent, and it’s a one and done job.

Insect netting isn’t just for caterpillars. It’s also great for keeping out other flying insect pests such as potato beetles and grasshoppers. Higher-quality netting with very fine mesh can even keep out smaller pests like leaf hoppers, which are known to transmit diseases to certain crops.

Now, insect netting isn’t 100% pest proof. I’ve yet to find a way to keep ground-dwelling critters like slugs and cutworms from finding their way underneath, so you’ll still need to keep an eye out for those. Still, netting will drastically reduce the amount of time you’ll have to spend fighting with pests (and the damage that inevitably happens despite your efforts).

I’ve been using this netting for our brassicas, potatoes, and greens for several seasons now with good results. I like the fact it comes in a large roll you can easily cut into sections to cover multiple garden beds.

Insect Netting and Pollination

When using insect netting, keep in mind that some crops need insect pollination to produce a good harvest. Squash, pumpkins, and most varieties of cucumbers are strictly insect pollinated, meaning they will yield exactly nothing if pollinators cannot access the flowers. Other fruiting crops, such as peppers, tomatoes, and okra, are wind-pollinated, but visiting pollinators still improve pollination and boost yields.

For crops that require or benefit from insect pollination, you’ll need to remove any netting once flowering begins. Root vegetables like beets and potatoes and any veggies you grow for the leaves or heads (greens, broccoli, collards) can stay under netting all season.

Frost Fabric

Late season frosts can come out of nowhere, despite your careful studying of the weather forecast when you make your planting plans. Even cold-tolerant crops such as cabbage, beets, and lettuce are vulnerable to damage from a heavy frost, when they’re still tiny or recently transplanted. If they survive, frost damage can lead to setbacks and cause heading or root crops to bolt (go to seed without producing a harvest).

Frost fabric is a live-saver when an unexpected cold snap comes. If your garden is already set up with hoops for row cover, it’ll take you ten minutes or less to cover young plants in the evening. Then, you won’t have to worry about walking out to damaged, wilted seedlings the next morning.    

Frost cover is also quite handy for extending your growing season into the fall and winter months. Many cool season veggies can survive some seriously low temperatures (even as low as the teens Fahrenheit) with cover. Frost cover allows you to keep your fall crops and any succession plantings producing later into the season.

Note: You don’t have to buy garden-specific frost fabric to protect your plants. Things like old sheets or blankets, tarps, and plastic sheeting will also work. The main benefit to the frost fabric meant for plant protection is its breathability. Since it allows some airflow while shielding from frost, you won’t have to worry as much about your plants overheating if you forget to remove it the next day.

When to Use It

We throw on the frost cover for young cool-season seedlings or recent transplants whenever lows are predicted to be below 40. Frost can happen at temperatures as high as 38 F. Covering young and vulnerable plantings is especially important if the temperature drops suddenly after a period of warm weather.

Most established cold-hardy plants don’t need cover for frosts and light freezes unless they have heads nearing harvest size (temps close to freezing may burn broccoli, cauliflower, and cabbage heads). However, many can take at least some damage from hard freezes. The safest bet is to cover even mature crops for temperatures dipping below the high 20s.  

It’s important to note that frost cover won’t always save frost-sensitive crops like tomatoes and squash from very cold temperatures. It may prevent damage from an unexpected light frost (35 to 38 F range), but a sub-freezing night will likely wipe them out even with cover. Don’t use frost cover as a failsafe for these crops. Make sure to wait until the threat of a serious cold snap is over before planting them!

Shade Cloth

This is one many folks don’t think about, but we use it every year in our garden to combat heat stress in sensitive crops. We grow in both the spring and the fall, and cool-weather crops really don’t enjoy those major temperature swings that come with the shoulder seasons in a lot of climates.

While a pepper or tomato plant might shrug off an 87 degree afternoon, temps in that range spell trouble for things like broccoli, cabbage, or potatoes. If the heat hangs around for more than a day or two, they may stall and catch disease, bolt prematurely, or, best case scenario, produce a lower-quality harvest. Too-high temperatures will cause bitterness in greens and lettuce, poor root or tuber development in potatoes and other root vegetables, and small, loose heads in heading vegetables.

Using shade cloth keeps both the air temperature and soil temperature considerably lower, in a covered garden bed, giving these crops a much better shot at pushing through a heat wave. It can also come in handy if temperature soar shortly after you’ve put out new transplants. Even summer crops can struggle to cope with high heat, if their roots aren’t good and established yet.

Shade cloth comes in different percentages based on how much light it blocks. For veggies, 40% shade cloth creates the ideal balance. It’ll shield sensitive plants from extreme heat while still letting in plenty of light for growth, meaning you can leave it up for days at a time if needed. Some gardeners in very hot climates with lots of sunshine prefer 50% shade cloth.

You can get shade cloth in either pre-cut “shade tarps” or in bulk rolls for covering more garden spaces. For using with hoop tunnels, I prefer the cuttable shade cloth that comes in rolls, since it can be cut to the exact size you need without fraying or unraveling. However, if you just have one or two beds to shade for now, individual shade tarps are a budget-friendly option.

When to Use It

Most cool season crops, like your root veggies, cabbage family crops, lettuce, etc., can have trouble with temperatures above 75 F, even if they don’t show obvious signs of stress.  

Our shade cloth stays out in the garden on standby all season long on our cool-season veggie beds. We keep it clipped to the hoop tunnels, ready to pull up as needed. Since it only takes a second, I’ll raise the shade cloth whenever temps rise more than a couple degrees above 70 on sunny days.

What about summer crops?

In our Zone 7 garden, our worst summer heat waves are usually short-lived and don’t often push temperatures above the high 90s. Summer crops like tomatoes, peppers, squash, and cucumbers may temporarily slow production, but otherwise, they can handle it without too much trouble.

Most summer fruiting crops grow quite large, meaning they won’t stay contained to our little hoop tunnels. For us, the hassle of figuring out how to cover 8 foot tall tomato plants with shade cloth isn’t worth it, just to prevent a few dropped flowers. However, if your summer temperatures are regularly well above 90 and into the triple digits during your growing season, finding a way to hang shade cloth for such crops can really increase your production.  

How Long Will Hoop Tunnels and Row Cover Last?

As far as the hoop tunnels go, rebar stakes will serve their purpose for, well, probably decades. They’ll get rusty, but they’ll still do the job. PVC wears out a bit quicker, but you’ll still get years out of it (especially if you can spend a few extra bucks for the Schedule 40 PVC conduit).

UV damage is the biggest factor that shortens the lifespan of PVC hoops. To limit their exposure and keep them going for longer, remove them from the garden when they’re not needed and store them in a shed, garage, or carport.

The same goes for row cover materials like insect netting, frost fabric, and shade cloth. The less unnecessary time they spend out in the elements, the longer they’ll stay in good condition. Insect netting is a bit fragile and tears easily if it snags on something. If it ends up with a random hole, though, you don’t need to replace it. Instead, I repair mine with window screen repair tape.

Hoop tunnels and row cover might be an extra step in getting your garden up and going, but it pays off in big ways. When you see the benefits of using it over a season, you’ll never go back to fighting a losing battle with insect pests and just hoping for the best when it comes to the weather.