Thornless Blackberry Production in High Tunnels

Thornless blackberries do not perform consistently in the Northeast. This has been attributed to both cold mid-winter temperatures and fluctuating spring temperatures. We have grown 4 cultivars of blackberry in a four-season high tunnel for six consecutive years, and with the exception of one year when we experienced rabbit damage, production has been several-fold higher than adjacent blackberries grown outdoors. Mid-winter temperatures and temperature fluctuations are not much greater inside compared to outside the tunnel, yet yields are much higher inside. Yields of 'Chester,' 'Doyle,' 'Triple Crown,' and 'Ouachita' increased for each of the first 4 fruiting years, then decreased slightly. Fruit size, ther percentage of marketable fruit, and length of harvest were almost always higher in the tunnel than outside. High tunnel yields approached 40,000 kg/ha with 'Chester' in the fourth fruiting year. Disease and insect problems were few. The biggest challenge is cane management and trellising as primocanes can grow several meters in length inside the tunnels. Experiments are underway to better determine how to manage such excessive primocane growth. An economic analysis of blackberry production was conducted, and showed that establishment costs were covered by the fifth year, and subsequent years could net a grower several thousand dollars per 9 x 30 m tunnel.