Inflorescence buds differentiate throughout spring, stop in summer, and resume in autumn. Flower morphology complete in the following spring, just before anthesis. In male and female trees, flowers are borne in compound racemes and paniculate inflorescences, respectively. The perigonium of the male flower and the perianth of the female flower contain 3-5 sepals. The female flower has no nectaries.
Pollen is distributed by the wind.
In female trees blooming lasts 3-4 weeks, whereas males shed pollen for a couple of weeks. Most of the male cultivars bloom earlier than the female. Thus, to guarantee an extended pollination period it is necessary to introduce into an orchard early, medium and late blooming males. Soon after fruit set, the hull and shell start to enlarge but the embryo becomes evident only 6-8 weeks later, when the cotyledons start to fill the nut. Six seven weeks before ripening, the suture along the two shells that form the endocarp starts to separate.