2017 ASHS Annual Conference

Maryland pick-your-own (PYO) growers are very concerned about the negative effects of increased seasonal temperatures. Peak PYO season is moving earlier in the summer as consumers try to avoid hotter August days. The heat and the market window shift presents growers with new challenges. Blueberries (Vaccinium corymbosum), raspberries (Rubus idaeus) and blackberries (Rubus spp. L.) are among the most popular, but blueberry production requires soil amendments to acidify the soils in Maryland; raspberry and blackberry cultivars must be thornless and produce large, firm fruit. Heat-tolerance and a requirement of an earlier harvest time increase the difficulty in choosing cultivars. A blueberry management trial and a blackberry propagation trial were initiated to answer growers’ questions. Northern highbush ‘Blue Ray’ and southern highbush ‘New Hanover’ blueberries were grown in a greenhouse in different soil compositions. Pots contained treatments of pure field soil, a ratio of 1:3 horse waste to soil, or soil with added gypsum. Gypsum was applied twice to the appropriate treatments at a scaled rate of 1 ton/acre. These treatments mimic common field growing conditions for PYO growers. Blueberry plants were evaluated after five months of being grown in their treatment based on soil pH and overall growth of the plant. In most cases, the barn waste amendment proved to be detrimental to plant health while gypsum applications encouraged plant growth. This matched growers’ previous observations. ‘New Hanover’ grew better than ‘Blue Ray’ plants, suggesting that ‘New Hanover’ is more resistant to upland soil conditions or heat. With increased seasonal temperatures, southern highbush blueberries deserve additional testing. Blackberries are naturally more heat tolerant than red raspberries. A “distinct thornless blackberry” cultivar, ‘Black Jack’ was released in 2013 (USPP25433 P3). Its potential has not been widely explored due to a lack of available plants for study. An exploratory propagation trial was initiated in 2016. This experiment was designed to test whether producing plants from cuttings could be done readily. Two-node cuttings were taken from young primocanes in July and grown out in a greenhouse. A high rate of mortality was experienced from high greenhouse temperatures. Leaf necrosis and unusual chlorosis was experienced during leaf growth but were not pathogen related. No plants have exhibited undesirable variations. True to type, ‘Black Jack’ can be asexually propagated by cuttings which allows for future field nursery production and research trials.