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Low tunnels can help extend growing season

STILLWATER, Okla. – For many people, there is not anything tastier than a vine-ripened tomato or fresh herbs picked right off the plant. Right now, gardeners across Oklahoma are enjoying fruits of their labor from their gardens.

However, once the weather cools down, it seems the fresh taste of summer goes away. And for those who have gone all winter without that fresh summer taste, it seemingly takes forever for the weather to warm up enough to start planting in the spring. Fortunately, there is a way for gardening enthusiasts to extend the taste of summer into the fall and early winter months or get a head start on spring planting.

David Hillock, Oklahoma State University Cooperative Extension consumer horticulturist, said low tunnels, or quick hoops, are essentially miniature greenhouses and can be used to grow vegetables, herbs, strawberries, and even cut flowers, into the winter months. They also can be used to get an early start on summer crops in the spring.

tunnel gardening.jpg“Some vegetables to consider for low tunnels in the winter include brassica greens such as collard, kale, turnip and mustard,” Hillock said. “If you want to get an early start on your spring gardening, warm season crops such as tomato, pepper, eggplant and cucurbits can be planted earlier than with traditional gardening.”

In addition, gardeners can construct their low tunnels to cover an entire garden bed or specific parts or rows of a garden.

You can use three basic types of materials to create the hoops, including PVC, electrical conduit and wire. There are advantages and disadvantages to all three. PVC is less expensive and easier to bend into the hoops, but the material tends to break down over time from UV exposure.

Metal frames are more expensive and need to be bent into shape, but the hoops themselves anchor directly into the ground, therefore eliminating the need for additional staking materials.

The least expensive material is a 9-gauge to 12-gauge wire bent into hoops. This material is useful for creating very low tunnels for crops such as spinach or lettuce. The good thing about making your own hoops is you can make them any size. Larger hoops allow for taller plantings, such as tomatoes.

Hillock said the spacing of the hoops will depend on wind protection of the planting site, and possibly the snow load. Spacing of 5 feet to 8 feet is adequate for PVC and metal hoops.

“Once your hoops are installed, cover the row with plastic. It comes in varying thicknesses with different light transmission qualities Be sure you get it tight enough to keep it from lifting in the wind,” he said. “Secure the edges of the plastic with bricks or sandbags.”

Do not forget about being able to access your garden after constructing the low tunnel. Easy access is important. This also is important for easy venting on warm days.

In most cases, keeping the low tunnels warm is not an issue. The tunnel itself will provide your plants all the protection they need from the cold weather. However, gardeners can place plastic milk jugs of water in the tunnel. As the sun shines during the day, the water will heat in the jugs. Then, during the night, the heat from the water bottles will help keep the temperature warmer inside the tunnel.

Avoid letting the tunnels get too hot on sunny days. Fortunately, low tunnels are easy to ventilate by simply removing the weights holding down the plastic and pulling up the plastic a bit to allow air to flow through. If the weather is especially warm, removing the plastic all together may be in order. Just make sure to put it back in the evening.

“Extending your growing season is relatively easy and inexpensive to do. For the most part, the materials are reusable from year to year,” Hillock said. “For those who want the fresh taste of a bountiful summer garden, build a simple low tunnel and you can start gardening earlier in the season, as well as garden later into the year. Depending on Oklahoma’s weather, you may be able to put fresh produce on your Thanksgiving table.”



Trisha Gedon
Communications Specialist
Agricultural Communications Services
Oklahoma State University
136 Agriculture North|Stillwater, OK  74078|
405-744-3625 (phone)
405-744-5739 (fax)

Oklahoma State University - Stillwater, OK 74078