2013 ASHS Annual Conference

Primocane fruiting blackberries are attractive to Kentucky growers because they can be grown organically and are able to produce a niche-market crop from late summer until frost. Therefore, locally produced fruit from primocane fruiting blackberry selections can be harvested from July until usually October, providing fruit for sale 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 (APF-153 T, APF-156 T, APF-158, APF-172 T, APF-185 T, APF-190 T, and APF-205 T) from the UARK 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 5 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 5 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 6–8 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 at 2559 lbs/acre. However, all other selections had yields that were much lower, ranging for 62–575 lbs/acre. APF-185 T had the largest average berry size at 4.6 g, while Prime-Ark 45® had the smallest berry at 3.0 g. The extremely high temperatures during June–September (over half the days had daily highs of 85 °F or higher), likely negatively impacted both yield and berry size on all selections. Year to year yield and fruit quality characteristics will need to be further evaluated and none of these advanced selections have yet been released for commercial production.