Patterns of flower-bud differentiation, development, and growth habits of several blueberry (Vaccinium spp.) cultivar types grown in Japan and New Zealand

Abstract

The time of flower-bud differentiation and development in relation to harvest time was examined in New Zealand and Japan by using 15 blueberry cultivars that belong to 4 types; half-high-, northern highbush-, southern highbush-, and rabbiteye - types. The numbers of flower buds and compactness in young plants were examined in Japan by using 17 cultivars that belong to the above 4 types. The cultivars were divided into 3 groups, depending on the time of flower-bud differentiation; (1) cultivars that differentiate flower buds mainly during the harvest period, i.e., half-high-type, northern highbush-type, and some southern highbush-types, (2) cultivars that start differentiating flower buds about a month after the end of the harvest period, such as some southern highbush-types, and (3) cultivars that differentiate flower buds after the peak of the harvest period, e.g., rabbiteye-types. In group (1), the period from flower differentiation to pistil formation was shorter in early-ripening cultivars than in late-ripening ones. The relationship between the time of flower-bud differentiation and that of harvest was almost similar in the southern and northern hemispheres. In New Zealand, however, anthesis in both 'O'Neal' and 'Reka' occurred immediately after harvest. Numerous flower buds formed on potted young plants of 'Bluebelle' (rabbiteye-type) and 'Sunshineblue' (southern highbush-type). 'Sunshineblue' and 'Tophat' (half-high-type) have a very compact vegetative profile.