For centuries a wide variety of techniques have been used to extend the growing season of horticultural crops. Glass jars, glass cloches, hotcaps, cold frames, hotbeds, and greenhouses of various types have all contributed to season extension. More recently, row covers and high tunnels have become popular with growers because of their simplicity and effectiveness in protecting crops from low temperatures in both spring and fall.
Row covers and high tunnels do not offer the precision of conventional greenhouses for environmental control, but they do sufficiently modify the environment to enhance crop growth, yield, and quality. Although they provide some frost protection, their primary function is to elevate temperatures a few degrees each day over a period of several weeks.
In addition to temperature control, there are also the benefits of wind and rain protection, soil warming, and in some instances control of insects, diseases, and predators such as varmints and birds. Overall, these growing systems should be considered protected growing systems that enhance earliness and higher yields, improve quality, and reduce the use of pesticides in some cases.
Row covers and high tunnels have sufficient versatility to make them useful on a wide diversity of crops and in various cropping systems. Vegetables, small fruits, and flowers are all suited to these growing systems; but the specific crops which might be grown will to a large extent depend on marketing opportunities for individual crops by individual growers.
High tunnels are not conventional greenhouses. But like plastic-covered greenhouses, they are generally quonset-shaped, constructed of metal bows that are attached to metal posts which have been driven into the ground about two feet deep. They are covered with one layer of 6-mil greenhouse-grade polyethylene, and are ventilated by manually rolling up the sides each morning and rolling them down in early evening. There is no permanent heating system although it is advisable to have a standby portable propane unit to protect against unexpected below-freezing temperatures. There are no electrical connections. The only external connection is a water supply for trickle irrigation. Dr. Otho Wells was a pioneer in promoting the use of high tunnels in the northeastern United States and developed the New Hampshire design and system of production that involved covering the entire soil surface inside the tunnel with a solid sheet of 6-mil thick plastic. At Penn State we re-designed the endwalls so that they can be raised up to facilitate easy access into the tunnel of a small tractor and tiller and a system of production that uses 18- inch wide raised plastic mulch covered beds with drip irrigation tape buried 2-3 inches beneath the bed. The raised mulch beds are 44 inches apart, which allows 4 rows in a 17 foot wide high tunnel.
At Penn State a tremendous amount of research and extension programming is oriented toward high tunnel production of vegetables, small fruits, tree fruits and flowers.
A High Tunnel Production Manual is available for purchase. Click here for more information.
- High Tunnel Manual
- "Production of Vegetables, Strawberries, and Cut Flowers Using Plasticulture NRAES-133"
- "Implementation of a BioControl Program for Insect Control in High Tunnels" Cost is $10.00 (includes tax).
- Green Production in High Tunnels [pdf]
- High Tunnel Cut Flowers [pdf]
- High Tunnel Construction [pdf]
- High Tunnel Technology [pdf]
Crop Specific Articles
- Production System for Horticultural Crops Grown in the Penn State High Tunnel [ pdf]
- High Tunnel Production of Cucumber on Raised Beds
- High Tunnel Garlic Variety Study
- High Tunnel Production of Lettuce using Paper Mulch, Bare Ground and Earth Boxes
- High Tunnel Tomato Variety Trial
General Information Articles
high tunnel publications
M.D. Orzolek Department of Horticulture PSU
Penn State High Tunnel Research and Education Facility Rock Springs, PA
M. D. Orzolek Penn State Center for Plasticulture University Park, PA
A Tool for Economic Development, Job Creation, and Increased Quality of Life through Urban Agriculture
Penn State High Tunnel Extension Program