Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Research was conducted on extending the production season for blackberries in Delaware. Primocane producing blackberries offer the potential for extended summer production and fall production for sales at farmers markets, and to schools, institutions, restaurants, and local wholesale outlets. Primocane fruiting varieties will produce on the current season’s growth from August through a frost. They have an added benefit of also producing a larger, substantial crop on floricanes that are overwintered and harvested starting the next June.
Two commercially available thorny primocane bearing blackberry varieties, Prime Jan and Prime Ark 45 were planted in 2011. Plots were harvested from August-November in 2012. A portion of these were left to fruit on floricanes in 2013 as well as on new primocanes in 2013.
In addition, five experimental fall-bearing thornless varieties from the University of Arkansas were planted in 2011. These plots were harvested from July through August in 2012. In 2013, all plots were fruited on both floricanes and on primocanes from June through October.
Yields for primocane production in 2012 were low across all varieties due to excessive heat. An experimental line, 158, had the highest primocane yields at 1,058 lbs per acre.
In 2013, floricane yields in the thorny variety Prime Ark 45 were over 16,000 lbs per acre with an additional 6,000 lbs per acre on the primocanes. This is twice the expected yield. Several experimental thornless varieties also had high total yields of over 20,000 lbs per acre (158 and 190T). The variety 153T, which has been commercially released as ‘Prime Ark Freedom’, had the largest fruit size at over 8 grams per berry.
The dual production system on both floricanes and primocanes is promising for extended production over an 18-20 week season from June through October. However, there was heavy pressure from Spotted Wing Drosophila in 2013 with this extended production. We expect several new thornless cultivars of primocane fruiting blackberries to be released in the next 3 years.