The seasonal progression of the reproductive phenology of two southern highbush blueberry (V. corymbosum L. interspecific hybrids) cultivars in the Western Cape, South Africa

The objective of this study was to evaluate the timing and duration of selected flower bud phenological stages of two southern highbush blueberry (SHB) cultivars in a Mediterranean climate to optimize the management of commercial production systems. The experiment was conducted in commercial orchards during the 2020 growing season, in the Hex River and Wolseley production areas, Western Cape, South Africa. The timing (date) and duration (days) of selected flower bud stages were recorded on individual plants, from April to November 2020 for bud swell, bud break, tight cluster, closed flower, open flower, petal fall, green fruit, colouring fruit, and fruit harvest respectively. Standard commercial management practices were followed on both sites. Cultivar 8-42 flowered from April to mid-October, with a peak during early August. Cropping occurred from early August to mid-November, and volumes peaked in October, at both sites. Cultivar 9-02 flowered from April to late October, with a peak during early August at the Wolseley site, whereas flowering for this cultivar only peaked during late September, at the Hex River site, indicating a possible climate related response. Subsequently, harvest started two weeks later at the Hex River site for ‘9-02’, while the highest yield volumes were obtained during October to early November, at both sites. This paper provides a first report on the phenological categorization of the reproductive development of commercial SHB blueberry cultivars, as produced in the Western Cape, South Africa. As all major management decisions in blueberry cultivation depend on the phenological phases of the crop, this information will contribute towards decision making regarding production, but also via quantifying the progression of each stage in addition to the peaks, allowing for additional logistical management. The influence of growing conditions on the phenological development of these cultivars was also explored and indicated the need for supplemental research considering the influence of micro-environmental conditions in driving evergreen production blueberry systems.