Rubis V. Bioecological peculiarities of North American hawthorns (Crataegus L.) in connection with their using in the green building in Forest-step of Ukraine

The thesis is devoted to investigation of bioecological peculiarities of 17 species, varieties and forms of North American hawthorns in the Forest-step of Ukraine. The rhythms of development, the peculiarities of blooming and fruiting of investigated species have been studied. It has been established, that phenological phases of most investigated species were characterized by constancy and coordinated with climate-weather conditions of zones of introduction.The concerning to light of the North American hawthorns have been determined and resistance to unfavorable environmental factors has been found, they're the high winter hardiness and drought resistance, resistance to gas and dust pollution, to pests and sickness has been marked. Optimum terms and ways of reproduction have been worked.The results of introduction of 17 species, varieties and forms of North American hawthorns in the Forest-step of Ukraine have been summarized. The ornamental qualities of investigated species are evaluated. The examples of compositions have been designed and the recommendations to practical use in the basic composite of landscape architecture have been given.