Mow-down and Tip Pruning Management of Primocane Blackberries in Coastal California

Fresh market blackberry (Rubus spp.) production is increasing in California largely in response to growing market demand. Newer primocane fruiting cultivars (Rubus subgenus Rubus Watson) enable annual mowing and may permit better targeting of market windows. California coastal production areas surrounding Watsonville, Santa Maria, and Ventura are important centers for blackberry production running north to south, but these areas have different temperature regimes that affect how plants respond to timing of off-season mow-down and subsequent pruning. Varying mow-down and tip pruning treatments were imposed on two-year old PrimeArk 45® blackberry plantings in Watsonville (2011 season) and Santa Maria (2012 season) and varying tip pruning on establishment year plants in Ventura, CA (2012 season). Mow-down periods for Watsonville and Santa Maria were the first week in January, March, or May and tip pruning was done at 0.45 m, 1.5 m, 0.45, and 1.50 m, and no pruning. Tipping (to 0.60 m) in Ventura was done April 23, May 31, or July 25. In Santa Maria, highest yield and the best timing of production resulted from January mowing whereas in the more northern Watsonville, harvest began one month later and highest yields were from March mown plants. The January and March mow-down plots were not markedly different at Watsonville however, and the response to mow-down timing was similar with May mow date producing later with lower yields at both Watsonville and Santa Maria. At Watsonville and Santa Maria, 0.45 tipping height produced more fruit than the other treatments at all harvest times and harvest periods were similar among tipping treatments. At Ventura, the May tipping produced higher yields and earlier harvest than earlier or later dates. Ventura plants were in the establishment year however, so the results may also represent plant size effects. Results suggest that at more northern coastal sites, mowing may be delayed until March whereas in Santa Maria, January pruning is better. Responses to mowing time and tipping were different at the different locations and warmer temperatures at more southern locations likely advance the optimum mowing time, response to tipping, and fresh fruit production period.