Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Until recently, commercially available blackberries were floricane types, that is, they fruit on last year’s canes. Six years ago, the University of Arkansas released their first primocane blackberries, Prime-Jim and Prime-Jan. Primocane blackberries fruit on current season canes, allowing for blackberry production from mid-summer through frost. In subsequent years they have the potential for two-season fruiting – in early summer on overwintered canes and as a late summer and fall crop on current season primocanes – as much as 6 months of production. The first two releases (Prime Jim and Jan) did not have sufficient fruit quality to be used for commercial production and were mostly recommended for home gardens. In 2009, Dr. John Clark at Arkansas released Ark-45, a primocane blackberry which did have good fruit quality and commercial potential. It is recommended for trial in Delaware. Unfortunately it is still thorny which will limit its use. The good news is that Dr. Clark is working on thornless primocane blackberries. We will be testing some of his advanced thornless primocane selections at the UD research station at Georgetown (planted this spring).
What is exciting about primocane blackberries is that they offer extended production potential into the fall. They also offer flexibility in production as they can be treated as a two season fruiting crop summer and late summer-fall (overwintered and primocane production) or single season (primocane only) production late summer-fall. Blackberries are generally well adapted to Delmarva conditions but will shut down if temperatures stay in the 90s for extended periods. Primocane blackberries will be flowering and fruiting much of the time in the cooler late summer and fall. Stay tuned as we follow these blackberry advances.