ОСОБЛИВОСТІ ВПЛИВУ ТЕМПЕРАТУРНИХ УМОВ НА ТЕРМІНИ ПОЧАТКУ КВІТУВАННЯ ПРЕДСТАВНИКІВ РОДУ MAGNOLIA L. І FORSYTHIA VAHL. В УМОВАХ БОТАНІЧНОГО САДУ ХНПУ ІМЕНІ Г.С. СКОВОРОДИ

Abstract

Botanical Garden of H.S. Skovoroda Kharkiv National Pedagogical University is located on the alluvial sands of the pine forest terrace of the Kharkiv river. This strongly complicates the formation of the plant collection, including selection of decoratively flowering tree species, resistant to such conditions. However, some representatives of genera Magnolia L. and Forsythia Vahl. were shown to be quite resistant to the conditions of this botanical garden. This prompted us to study of the influence of temperature conditions on the beginning of the flowering of these introduced plants. The research was carried out during 2013-2017. Five specimens of Forsythia suspensa and Magnolia × kewensis grafted on M. × loebneri were included in the study. The phenology of flowering was studied by methods of M.E. Bulygina and I.M. Beideman. To check the dependence of the beginning of the flowering from the sum of the positive temperatures of each month, the nonparametric Spearman correlation coefficient (r s ) was used. As a result of the study it was shown that the sum of positive temperatures of January, fluctuating from 2°C to 10°C, is not decisive for the date of M. × kewensis beginning of flowering. Instead, the sum of the positive temperatures of February, fluctuating from 29°C to 83°C, had the greatest positive effect on the period of the flowering: the higher was the temperature of February, the earlier M. × kewensis began the flowering. The sum of positive temperatures in March, fluctuating from 74°C to 294°C, again, almost did not affect the date of the hybrid's start of flowering. Finally, the temperature of April, which ranged from 124°C to 313°C during the period from 1.04 until the start of M. × kewensis flowering, paradoxically showed the highest negative effect on the date of flowering beginning. We can assume that the high temperatures of April inhibit the early start of flowering of M. × kewensis , contributing to dehydration or thermal burn of the plant. For the flowering of F. suspensa the sum of positive temperatures in January and February we almost unaffected. But, unlike M. × kewensis , the sum of positive temperatures in March has a significant effect on the flowering of this species. As for the temperatures of April, the same as for M. × kewensis , for F. suspensa the slowdown in the beginning of the flowering was observed in the years when the sum of positive temperatures of this month reached the highest values. It is also clear from the obtained data that the sum of positive temperatures for the entire investigated winter-spring period does not correlate with the period of the beginning of M. × kewensis and F. suspensa flowering. Key words: dendroflora, introduced species, open field cultivation, landscaping, sum of positive temperatures, phenological observations .