Flowering phenology and pollen seasons of Corylus spp. in Lublin (Poland), 2008-2011

In the years 2008-2011, phenological observations of flowering of male inflorescences were carried out in seven taxa from the genus Corylus: C. americana, C. avellana, C. avellana ‘Contorta’, C. avellana ‘Pendula’, C. × colurnoides, C. cornuta, C. maxima, grown in the Maria Curie-Skłodowska University Botanical Garden in Lublin. Simultaneously, the hazel pollen seasons in the atmosphere of Lublin were analysed using a Durham sampler. The aim of the work was to assess the flowering in seven Corylus taxa in relation to selected meteorological elements and to describe the pollen seasons in the years 2008-2011. During the study years, the annual phenological cycles in the studied Corylus taxa differed markedly in terms of timing of the onset of the successive flowering phases. During the four years of observations, the earliest beginning of hazel flowering was found at the end of January, whereas the latest – at the end of March. The earliest full bloom took place in the first decade of February, and the latest – in the first decade of April. The end of flowering was reported in February or in the first or second decade of April. Each year, C. avellana was the first to produce flowers and it was subsequently followed by C. americana, C. × colurnoides, C. maxima, C. avellana ‘Pendula’, C. avellana ‘Contorta’, and C. cornuta. The pollen seasons in the study period began at the end of January, in the second decade of February, or in the first decade of March. The end of the pollen seasons most frequently took place in the first or second decade of April. The length of the pollen seasons ranged from 38 to 49 days, while the length of the flowering periods in the individual taxa was 22 days on average. During the four study years, the onset of flowering in C. avellana and the beginning of the pollen season coincided on the same day, whereas the onset of flowering in the other taxa was usually reported after the beginning of the pollen seasons. The flowering period of C. avellana ‘Contorta’ and C. cornuta lasted from 5 to 16 days after the pollen season. The development of inflorescences was most closely related to maximum temperature and relative air humidity