Yield Performance and Cold Hardiness of Advanced Thorny and Thornless Primocane-fruiting Blackberry Selections at Kentucky State University

Kentucky growers are interested in primocane fruiting blackberries because they can be grown organically and are able to produce a niche-market crop from late summer until frost. Locally produced fruit from primocane fruiting blackberry selections can be harvested from July until October, providing an extended season for fruit sales at farmers’ markets, community supported agriculture, and organic markets. In June 2011, a blackberry variety trial was established at Kentucky State University (KSU). Plants of the commercially available primocane-fruiting cultivar ‘Prime-Ark® 45’ (thorny erect, primocane-fruiting) and the Arkansas Primocane-fruiting (APF) selections of thorny or thornless (T) advanced selections (Prime-Ark® Freedom, APF-156 T, APF-158, APF-172 T, APF-185 T, APF-190 T, and APF-205 T) from the University of Arkansas blackberry breeding program, were planted at the KSU Research and Demonstration Farm, in Frankfort, KY. Plants were arranged in a randomized complete block design, with 4 blocks, including five plants of each cultivar per block (total of 20 plants of each cultivar) in a 10-foot plot. Spacing was 2 feet between each plant, and 5 feet between groups of five plants. Rows were spaced 14 feet apart. This trial was planted on the certified organic land and managed with organic practices following the National Organic Program standards. Weed control was achieved by placing a 6- to 8-inch deep layer of straw around plants, adding straw when necessary and hand weeding. Plants were irrigated weekly with t-tape laid in the rows. Primocane fruit production began in late July or early August for most selections. APF-158 had the highest yield in 2013–14 at 7147 and 3458 lbs/acre, and Prime-Ark® Freedom had the lowest at 760 and 648 lbs/acre. Prime-Ark® Freedom had the largest average berry size at 6.3 and 6.7 g. All selections experienced severe die back during the 2013–14 winter; however, APF-190 T had the lowest cane death at 64%. Year to year yield and fruit quality characteristics will need to be further evaluated.