Low tunnel hoops are one of my favorite ways to extend the homegrown harvest in my vegetable garden as well as protect my crops from pests. These compact structures are just miniature greenhouses and are quick and easy to build. I make mine from easily sourced materials like PVC conduit or 9 gauge wire and top them with an assortment of lightweight covers. Keep reading to learn how you can use low tunnel hoops to maximize production in your vegetable garden.
What are low tunnel hoops?
A low tunnel hoop is a handy garden structure made from two components; hoops and a cover. These can be used in spring, summer, fall, and winter to protect crops from weather. I also use them to reduce damage from large and small pests like deer, cabbage worms, and flea beetles. I’ve been using them for the past two decades and they’ve been a game changer in my garden. In fact I wrote a book on my garden covers called Growing Under Cover which includes detailed information on building and using low tunnel hoops.
Benefits of using low tunnel hoops in a vegetable garden
There are many benefits to using low tunnel hoops. I first began using them to extend the harvest of cool and cold season vegetables in autumn. They’re an easy way to get an extra 6 to 8 weeks from crops like arugula, bok choy, parsley, and winter lettuces. I later discovered that I could push the harvest even further into winter with hardier crops like tatsoi, leeks, kale, and endive.
Another reason to build tunnels is give heat-loving vegetables like tomatoes, peppers, melons, and eggplants a good start in spring. The unsettled temperatures of late spring can damage tender crops and a low tunnel is an effective way to capture sunlight and protect them the first few weeks after planting. Low tunnel hoops can also be put to work in summer when the weather is hot and dry and you’re trying to establish successive crops or vegetables for autumn and winter harvesting.
Finally low tunnel hoops reduce pest damage from large and small pests. My garden is visited by deer, rabbits, groundhogs (woodchucks), and squirrels as well as flea beetles, cabbage worms, and Colorado potato beetles. Using low tunnels means less work for me and healthier, more productive plants. Just remember covers for pest protection should be installed before the pests are a problem. Installing them once you’ve spotted cabbage worms or flea beetles may trap the pests beneath the cover with their favorite food.
How large are low tunnel hoops?
You can make low tunnel hoops to match the length and width of your garden beds. My raised beds are 4 feet across and 8 or 10 feet long so I make low tunnels to fit my beds. You can make narrower tunnels that are 3 feet across or larger ones that are 5 or 6 feet across, depending on the size of your beds. Plant size also plays a factor. For tall crops like kale or broccoli you’ll want to use PVC or metal hoops which create tunnels about 3 feet high. For lower growing salad greens or root crops you can use compact wire hoops to make shorter tunnels. If you don’t want to DIY low tunnels you can also source kits online and at garden centers.
Materials for the hoops
There are many materials that can be used to build hoops for low tunnels. I use three types: 9 gauge wire, 1/2 inch PVC conduit, and 1/2 inch metal conduit (EMT).
- 9 gauge wire – This easily sourced material comes from my local hardware store, often in 50 foot lengths. I use wire or bolt cutters to clip the 9 gauge wire into the desired length.
- PVC conduit – You can use various diameters of PVC conduit to make low tunnel hoops but I find 1/2 inch diameter PVC is both easy to bend and strong. It’s available in 10 foot lengths from hardware or building supply stores.
- Metal conduit – I also use 10 foot lengths of 1/2 inch diameter metal conduit to make heavy-duty tunnels, perfect for winter harvesting. Unlike PVC conduit, metal conduit can’t be bent by hand to form a hoop. You’ll need a metal hoop bender to create the U-shaped hoop.
Materials for the covers
I choose the cover for my low hoops based on two factors: the season and the reason for the cover. There are four types of covers I use in my garden:
- Polyethylene – This is the standard cover for my early spring, autumn, and winter low tunnel hoops. Poly is durable and allows excellent light transmission. I’ve experimented with many types of poly including construction and greenhouse grade. Construction grade poly is widely available and inexpensive. Unfortunately it’s thin and not UV stabilized and therefore tends to break down in the garden after just a month or two. Because I am trying to use less plastic in my garden I want to avoid materials that don’t last long. This is why I now use greenhouse grade polyethylene on my mini tunnels. It’s a resilient UV stabilized material that can last 4 to 5 years.
- Row covers – A row cover is a lightweight fabric-like material also called garden fleece, Agribon, or Reemay. There are various weights and sizes available to gardeners and row covers can come packaged or in a roll. Lightweight row covers offer several degrees of frost protection. Learn more about row covers and row cover hoops in this detailed article.
- Insect mesh or netting – Mesh cloth or insect netting is a cover used to deter pests from munching on your vegetables. For insect pests use mesh covers with tiny holes. For larger pests like deer or rabbits, you can use deer or bird netting.
- Shadecloth – Shadecloth is a versatile woven material that can be used in spring or summer to delay bolting of leafy greens or create shade to encourage seed germination.
How to make low tunnels
It’s quick and easy to make low tunnel hoops in the garden. Start by gathering your materials. If using lengths of 9 gauge wire for your hoops, bend each wire piece into a u-shape. Insert the ends of the hoops into the soil, pushing the wire several inches deep to make sure the hoop is secure. Space the hoops about 18 to 24 inches apart.
To make a low tunnel from PVC conduit follow the same procedure as for a wire tunnel, but space the hoops 2 1/2 to 3 feet apart. If you find it difficult to insert the ends of the PVC conduit into the ground, use 1 foot long rebar stakes to secure the hoops. Pound the rebar about 5 to 6 inches in the ground and slip the ends of the PVC overtop the stakes.
For a metal conduit low tunnel, start by bending the metal. Be sure to follow the instructions that came with your low hoop bender. Once you have the u-shaped hoops, insert the ends into the garden bed, pushing them down at least 6 inches into the soil to ensure sturdy hoops. Also use rebar stakes for metal conduit hoops if your soil is compacted or clay-based.
Keep covers securely attached to conduit hoops with snap clamps. Or, weigh down the ends and sides of low tunnel hoops with sandbags, rocks, lumber, or other heavy objects.
How to use low tunnel hoops year-round in the garden
There isn’t a day of the year I don’t have at least a couple of low tunnel hoops in my food garden. Below you’ll find suggestions of how you can use them in spring, summer, autumn, and winter to give your crops a good start in the garden, protect them from cold or hot weather, or prevent pest damage.
- Use a polyethylene or row cover for frost and weather protection of cool season crops planting 4 to 8 weeks earlier in the season.
- Pre-warm the soil a week before transplanting heat-loving vegetables like tomatoes and peppers. Top hoops with a polyethylene cover.
- In late spring use shade cloth to delay bolting in salad greens like lettuce, arugula, and spinach.
- A low tunnel covered in insect mesh is an easy way to reduce damage from pests.
- When the summer weather is hot and dry, use a length of shadecloth or row cover fabric to help establish successive crops or fall and winter vegetables. The shade reduces soil water evaporation and the temperature beneath the cover.
- Insect mesh floated on hoops is an easy way to prevent damage from large and small pests.
- As the weather cools in mid to late fall use a row cover or polyethylene sheet for frost protection.
- Unfortunately many pests don’t take a break at the end of the season. I use insect mesh to keep pests like cabbage worms from devouring my fall cabbage and broccoli plants.
- Winter calls for serious covers so I top my low tunnel hoops with a layer of row cover. Eventually I cover the row cover with sheets of polyethylene. The combination of row cover and plastic cover ensures adequate protection for my winter vegetables.
Caring for vegetables in low tunnels
When growing vegetables beneath garden covers there are a few tasks to consider. Watering and venting are at the top of the list, especially when using covers, like polyethylene, that isn’t permeable.
- Watering – When using covers like insect mesh or row cover, rain can pass through to the soil and irrigate crops. This isn’t the case when using poly covers, so you’ll need to pay attention to soil moisture, watering when necessary. A long handled watering wand makes quick work when watering a low tunnel. I often remove poly covers on rainy mild days in spring or autumn. This allows Mother Nature give the bed a good soaking. In my cold climate I don’t water tunnels in winter, but those in milder regions will have to monitor the soil and water occasionally.
- Venting – Venting low tunnel hoops promotes good air flow and reduces the temperature beneath the cover. This is essential on mild days when the inside temperature of a tunnel can rise quickly. Vent by lifting up the ends of the tunnel, or if the weather is very mild, pull the entire cover off to the side. If the night temperatures are expected to drop replace the covers by late afternoon.