Abstract

The article presents generalized scientific researches and experimental data on the bioecological peculiarities of the North American species of the Juglans L. genus. The peculiarities of the seasonal rhythm of development are revealed. Juglans cinerea L., J. rupestris Engelm. and J. major (Torr.) A. Heller were the first to wake up and J. nigra L., J. californica S. Wats., and J. hindsii (Jeps.) Jeps. ex R.E. Sm. wake up a little later. The biorhythm of woody plants is closely related to the increase in the sum of active (+10°C) and effective (+5°C) temperatures. Juglans cinerea and J. rupestris require the smallest sum of effective temperatures for buds swelling, that is 28.9 and 34.1°C, respectively; J. hindsii require the largest sum of effective temperatures -57.1°C and J. nigra require 50.6°C. Investigation of growth dynamics shows that intensive growth of all species of the Juglans genus was observed in May-June. The vegetation period in all Juglans species lasts 183-206 days. The development cycle of North American walnuts under research conditions is shifted towards the summer-autumn period. When determining frost resistance, it was found that the species are characterized by an average degree of subfreezing. All species genus are promising for use in ornamental horticulture of the Right-Bank Forest-Steppe of Ukraine, as evidenced by the full acclimatization of J. nigra and J. cinerea, good acclimatization of J. rupestris and J. major and satisfactory acclimatization of J. сalifornica and J. hindsii. It is established that J. nigra are promising for the development of highly productive forest plantations.