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Hazelnut (Corylus avellana) is a monoecious, dichogamous plant species that flowers in winter and early spring. In traditional hazelnut growing regions, hazelnut cultivars generally express protandry where the male flowers bloom before the female flowers. Nut set requires that compatible pollen be shed when the stigmas of the main cultivar are receptive. In this study, the floral phenology and date of leaf budbreak of five selections and 19 hazelnut cultivars from Europe and North America were observed over four years in southern Ontario, and results were compared with cumulative growing degree days. In the continental climate of southern Ontario, most cultivars showed protogyny. Flowering dates varied over the years with pollination occurring in a period of 2 - 3 weeks in early spring. These cultivars were classified into early, mid, and late blooming types. A growing degree day model was a better tool than average daily temperatures to predict the flowering dates of catkins and female flowers. Averaged over years, most of the cultivars in this study have a female bloom that is likely too early for the pollen shed by most of the other cultivars. This would likely impact yields in a commercial orchard. However, ‘Jefferson’, ‘Gene’, and ‘Epsilon’ have late females that are receptive when other cultivars are shedding pollen.

SummaryIn South-western Ontario's continental climate (short days, hot

The global demand for hazelnuts is increasing steadily, driven by chocolate companies, pharmaceuticals, health products, and others. However, North America only produces 5% of the world crop, of which 99% is produced in Oregon (USA). Most available cultivars are adapted to areas with mild winters and thus do not perform well in Ontario. Our objective was to identify genotypes capable of supporting the newly formed hazelnut industry in southern Ontario. In the last several decades, selections have been identified in Ontario, New York (NY) and Michigan (MI) that may be better adapted in Ontario than cultivars from Europe and Oregon. To test our hypothesis that these new selections would outperform cultivars from Europe and Oregon in southern Ontario, two trials were performed to evaluate yield, nut quality and winter hardiness. As hypothesized, selections from Ontario and NY such as ‘Gene’, ‘Alex’ and ‘Slate’, were winter hardy and highest yielding, followed by ‘Butler’, and ‘Gamma’ from Oregon. However, these selections did not perform well in other assessed parameters, such as nut quality and catkin survivability. Possible explanations for the poor performance of the European and Oregon cultivars include: 1) longer time needed to acclimatize and enter production phase relative to selections from Ontario, NY and MI; and 2) cold susceptibility during the initial establishment phase. The need to allocate resources towards survival probably delays the ability of the European and Oregon cultivars to enter the production phase. In conclusion, hazelnut cultivars brought from regions with a different climate need to be tested for cold hardiness.