High tunnels are polyethylene covered shelters being used in the vegetable industry to advance or extend the harvest season for many high value crops. Unlike traditional greenhouses, no supplemental heating is used in high tunnels. Brambles(raspberries and blackberries) are high value fruits that have good economic potential on small farms, but under Iowa conditions, they are not without risk. Traditionally, both crops are produced on biennial canes that grow vegetatively the first season (primocanes), and fruit in the second growing season (floricanes)
