Pruning and Training Systems Impact Yield and Cold Hardiness of ‘Marion’ Trailing Blackberry

The floricane-fruiting, trailing blackberry ( Rubus L. subgenus Rubus , Watson) cultivar Marion was evaluated in two plantings for the impact of floricane pruning date. This included leaving the dead canes unpruned and training new primocanes over the dead wood (new-over-old), primocane topping and suppression date in alternate year (AY) and every year (EY) production systems at various planting densities. The presence of primocanes during fruit development did not affect yield of the floricane in the current season but suppressing primocanes to June 30 in Oregon, USA, led to insufficient time for primocane growth, reducing yield of the floricane the following year by 36% relative to no primocane suppression. Pruning out senescing floricanes immediately after fruit harvest or later—thus allowing more time for remobilization of nutrients or reserves—had no impact on yield. However, yield in the new-over-old system was higher, likely due to less training damage to primocanes in this treatment. All of the AY treatments studied led to lower berry weight compared to EY production but this has not been an issue in the processed fruit market to date. Plants in AY production produced more canes per plant than in EY but at the industry standard spacing of 1.5 m, AY plants yielded only 60% to 66% more than EY plants in these studies, despite evidence of plants in AY production having greater cold hardiness. There was no significant effect of planting at higher density (0.6 and 0.9 m) on cumulative yield over 4 years. However, planting at 0.6 m and topping the primocanes to the top trellis wire (1.8 m) increased yield significantly compared to other AY treatments. This alternative production system may offer economic advantages to the 1.5 m EY or AY production systems through reducing management costs and allowing for mechanical pruning and training.