NC State Extension Publications


High tunnels are semi-permanent structures made of steel pipe arches and covered with polyethylene plastic to create a protected environment for plants. Raspberries and blackberries benefit from growing in high tunnels, which can extend the harvest season, improve fruit quality and yield, and enable growers to harvest fruit when it is raining (Figure 21). The tunnels are 10 to 15 feet high and 20 to 30 feet wide. Assembling tunnels side-by-side to cover areas of several acres adds some stability against wind damage. Plastic is typically used, and it is rarely in place on a given tunnel for more than one to three years. In cooler locations, end walls can be used to retain heat during the fall when nighttime temperatures can damage fruit.

In most eastern US systems, a primocane-fruiting raspberry produces fruit in mid- to late summer and fall for three to four growing seasons. At the end of each growing season, the canes are mowed to the ground. To prevent damage to the tunnel during the windy winter season, the plastic is often temporarily removed. In the western United States, a shorter intensive cropping system is used whereby plants are in the ground 18 to 24 months, and fruit is produced on both primocanes and floricanes.

Studies in North Carolina and Arkansas have shown that primocane-fruiting raspberry cultivars grown in tunnels resulted in high yields during the first growing season. Compared to field-grown raspberries, tunnel-grown yields were 30% greater or more, depending upon location and growing conditions. In cold winter locations, tunnels may also extend the normal summer harvest season into the fall.

Production practices for blackberry tunnel production are still in the developmental stages. In North Carolina, tunnels did not result in significantly greater yields or an increase in desirable post-harvest attributes. Primocane-fruiting blackberries have done well in tunnels in the western United States, but they did not perform well at high elevations in North Carolina due to early season frosts.

Figure 21.

Figure 21. Floricane-fruiting blackberries (right) and raspberries (left) in a high tunnel.

Absalom Shank, NC State University


Extension Specialist (Small Fruits)
Horticultural Science
University of Arkansas
University of Tennessee

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Publication date: Nov. 2, 2015

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