Growers often want to recoup some of the cost of a new planting of Southern Highbush Blueberry (SHB) by harvesting the fruit from the newly-planted bushes rather than stripping it off, a practice commonly recommended to allow the plants to become established. Researchers in Argentina wanted to test the effects of early cropping on SHB and see if this really is detrimental to the plants in the long run.
‘Star’ and ‘O’Neal’ cultivars of SHB were chosen to test because the first is very vigorous and the second is medium to low vigor. Four treatments were established on potted plants: 1) Control with 100% of flowers removed for the first two years after potting; 2) 100% flower bud removal the first year and 50% flower bud removal the second year; 3) 50% flower bud removal the first year and 0% flower bud removal at the second year; and 4) no removal of flowers buds during the first two years after planting. Flowers were not removed from any treatment in the third year. The number of shoots, number of leaves, total leaf area per plant, number of flower buds, number of fruits, annual fruit yield per plant, and cumulative fruit yield per plant were measured annually. Fruit yield was the number and weight of fruit at harvest. At the end of the third year plants were destructively harvested for dry weights of the various plant parts.
Early cropping did not negatively affect vegetative or reproductive growth or cane or root crown dry weights for either cultivar by the third year. However, flower buds at planting were removed for those treatments by pruning, which also removed some vegetative growth and may have set plant growth back. Flower buds were removed by hand in the second year. High crop load during the first year did not reduce fruit yield the second year. However, high crop load during the second year reduced fruit yield the third year. The most productive treatment for cumulative yield did differ somewhat by cultivar. Vigorous ‘Star’ plants responded with the highest cumulative yields with treatment two – 100% flower buds removed the first year and 50% the second. Less vigorous ‘O’Neal’ cumulative yield was highest with plants with 50% flower bud removal the first year and none the second. Although yields were highest in the third year if flower buds had been removed the first two years, cumulative yields were highest with some early cropping. Thinning of flower buds by pruning in the first year does not seem to be needed, but some thinning of flower buds in the second year will ensure a higher crop in the third year after planting. Thinning all flowers for the first two years or leaving all flowers on for the first two years resulted in the lowest cumulative yields.
Effects of Early Cropping on Growth and Yield of Southern Highbush Blueberry Cultivars (Vaccinium corymbosum L. Interspecific Hybrids) by M.P. Borda, M.A. Pescie, and N.F. Gariglio. Journal of the American Pomological Society 72(4): 222-230. 2018.