Winter Growing & Season Extension

Basic High & Low Tunnel Components

Protect Your Crops • Basic High & Low Tunnel Components

High Tunnels, Low Tunnels, Row Covers & Mulches

Protected cropping is the single biggest trend in horticulture today. High tunnels, low tunnels, row covers, and mulches can be used to protect crops from bad weather. Protected cropping can extend the season for months, while increasing yields and improving quality of vegetables, fruits, herbs, and flowers.

High Tunnels / Hoophouses

The ultimate tool in protected cropping is a high tunnel (also called a hoophouse), which is an inexpensive, unheated greenhouse erected right in the field. Hoophouses are quickly becoming an essential component of most produce and flower farms. A single layer of greenhouse poly over metal or PVC hoops, tall enough to walk into, provides an amazingly different growing environment. Hoophouses don't need electricity or heating systems, although some growers do add them to extend the season even further. In general, though, roll-up or roll-down sides are used to ventilate a hoophouse, and the sun does the work of heating it. Johnny's offers a line of professional-grade high tunnel kits to make construction more straightforward for DIY'ers.

Some of the crops that are commonly grown in a hoophouse include lettuce and greens, early and late in the year; strawberries in spring; raspberries and tomatoes in summer; and spinach and other cold-hardy vegetables over the winter. Many other crops will benefit from the protection, depending on regional variations. With careful crop selection, a hoophouse can be the most productive land on a farm.

Low Tunnels

Another protected cropping tool is a low tunnel. Low tunnels are made of small metal or PVC hoops, pushed into the soil over a bed of crops, and covered with spun-bonded polypropylene row covers. We've found that hoops fashioned from EMT (electrical metal conduit) are much sturdier and longer-lasting than those made of other materials, and thus more economical across time.

Low tunnels warm the soil and protect plants from frost and wind. They can be used early in spring for cool-weather crops, in late spring to give a head start to warm-weather crops such as tomatoes and peppers, and again in fall to keep cool-weather vegetables growing longer. They also are useful for protecting crops from predictable insect pests such as flea beetles and cabbage moths.

Using a low tunnel within a high tunnel is useful in cold climates to keep the soil from freezing until the dead of winter. Although plants stop growing when the days are short in mid-winter at higher latitudes, cold-hardy vegetables such as carrots and spinach can be harvested nearly all winter in this system.

Row Covers

Row cover alone can be pulled over crops to save them from untimely frosts. Late and early frosts are often one-night affairs; protecting against those relativel short-lived dips in temperatures can keep crops alive for several additional weeks of good growing conditions. Most growers keep a supply of row cover on hand for just such emergencies.


Plastic or paper mulches are another component of protected cropping systems. Black solar mulch warms cold soil; white-on-black mulch keeps soil cool. Biodegradable and paper mulches eliminate the need to take them up at season's end. All types suppress weeds, reducing labor.

Learn More

By employing some or all of these protected cropping systems, growers can take some of the risk out of farming and gardening.

For more ideas about hoophouse production, browse our extensive Season Extension Library.

Lynn Byczinski's book, The Hoophouse Handbook, is another one of our favorite resources.

About the Author
Lynn Byczinski
Lynn Byczinski,
Author & Founder of Growing for Market
Lynn Byczynski was growing organic vegetables and cut flowers for market when she decided to create a magazine that would help market gardeners nationwide share experiences and information. Her first issue of Growing for Market appeared in January 1992, and GFM has been published continuously ever since, becoming renowned in the market-gardening world for realistic articles that provide practical, how-to information about growing and selling produce and flowers.

Byczynski and her family have been growing vegetables and cut flowers since 1988, selling through CSAs, at farmers' markets, to chefs, grocery stores, and florists. They currently grow cut flowers and hoophouse tomatoes on about 2 acres of their 20-acre farm near Lawrence, Kansas.

She is also the author/editor of two of our favorite books about market farming, The Flower Farmer and The Hoophouse Handbook.