Phenological reaction of vascular plants to the extreme thermal regime in autumn–winter of 2019 in Ukraine

In the autumn and early winter of 2019, the weather in Ukraine was abnormally warm. For that period, numerous reports on unusual flowering of many species of plants in various regions of Ukraine have been received. This information on the established phenological reaction as a response to such extreme conditions was collected during November–December 2019 and analyzed by several indicators. The phenomena of phenological reaction at different stages of flowering have been recorded for over 80 species of plants in Ukraine. The species composition, taxonomic and fractional affiliation of species, their life forms and flowering periods during the normal season of vegetation according to the literature data have been established. The groups were determined by the duration and types of flowering. The most cases of flowering during the studied period were recorded in Zaporizhzhya, Transcarpathian, Kyiv, Odesa, and Rivne administrative regions of Ukraine, mainly in cities and other settlements. The largest number of phenological reactions were observed in the families Rosaceae (more than 20 species, for most of them re-flowering was recorded), Asteraceae, Amaryllidaceae, and Violaceae. Among life forms, phanerophytes and hemicryptophytes were generally prevalent. Most of phenological reactions were found for native, alien or introduced plant species in cultivation sites (botanical gardens, private plots, urban green plantations, etc.). Among species of alien plants, phenological reactions were observed more frequently than in native ones. The largest group is the re-flowering plants, which mainly includes species that have passed and completed the full generative cycle in spring of that year (Galanthus nivalis, Scilla bifolia, Ficaria verna, Iris pumila, Bellis perennis, Syringa vulgaris, Fragaria vesca, etc.), or their fruiting and seed fall ended in August–September (Persica vulgaris, Armeniaca vulgaris, Malus domestica, Prunus cerasifera, etc.). The most abundant is the group of early-flowering species that include introduced winter-blooming in the primary range Viburnum farreri, Viburnum × bodnantense which begin vegetation within their native range in December.