Method for Producing Long-cane Blackberry Plants

Blackberry plants have been propagated by tip-layering, soft- and hard-cane cuttings, root cuttings, and tissue culture (TC).  In the last 20 years, long-cane blackberry plants for off-season fruit production have become popular.  Long-cane blackberry plants have been produced from TC-plug plants that could yield as many as 20,000/ha of bare-root plants with four 1.5-m-tall canes.  However, this system requires that the field be replanted annually with 8,000 fresh TC plug plants.   A modified rotating cross-arm trellis system was used to produce over ~120,000 1.5- to 2.0-m-long cane ‘Triple Crown’ and ‘Siskiyou’ plants from stock plants established at a density of only 1,700/ha.  Lateral canes that develop from horizontally trained primocanes were trained to grow upward on the wires positioned on a slanted cross-arm trellis and then down to the ground.  Tips of lateral canes were inserted into pots for induction of adventitious roots.  After 4 weeks, the entire lateral cane was detached from the stock plant and the proximal end also inserted into a moistened medium.  Rooting occurred at that end.  With this procedure, 3-m-long cane plants with roots at both ends of the cane were generated.  Rooted cane plants were chilled and then grown in a greenhouse maintained at 17 to 22 °C during the day and 14 to 16 °C at night.  In both cultivars, 70% of buds broke.  Inflorescences developed on 68% and 46% of shoots on ‘Siskiyou’ and ‘Triple Crown’ cane plants, respectively.   Each inflorescence produced over 5 fruit averaging 7.1 g/fruit.  Additional studies are needed to determine the effect of longer exposure to cold temperatures and dark, cold-room storage on the performance of long-cane blackberry plants.   The cold-stored, containerized long-cane blackberry plants have potential for late-season fruit production.   Additional methods of producing long-cane blackberry plants will be discussed.