Features of seasonal growth of Arundo donax var. versicolor Mill. (Stokes) in the conditions of the M. M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine

Purpose. To define of phenological and morphological features of A. donax var. versicolor growth during the introduction in the M. M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine (NBG). Methods. The object of research was the plants of A. donax var. versicolor in the collection of ornamental grasses of the department of flower and ornamental plants of NBG. The plants were grown on a sunny experimental area during 2014–2020. Since under NBG conditions, A. donax var. versicolor did not enter the flowering phase, the beginning of the phases of spring regrowth, leaf unfolding, and the end of the growing season were recorded. Morphometric parameters and shoot-forming ability were investigated for 3–5 years of cultivation. Results. The beginning and duration of the phases of shoot spring regrowth and the unfolding of leaves of A. donax var. versicolor as well as their dependence on the sum of effective temperatures was established. Thus, spring regrowth begins with renewal buds on May 11 ± 5 days at the effective temperature sums of 226.6 ± 19.7 °С. The phase of leaf development in plants occurred on May 20 ± 7 days. The effective temperature sum at the beginning of this phase was 309.45 ± 11.66 °C. The productivity of shoot formation (1.6 ± 0.3 shoot per plant) under the conditions of introduction was determined. Conclusions. A. donax var. versicolor plants did not have a full cycle of seasonal development in the conditions of the NBG. Plants formed vegetative monocyclic shoots 240–260 cm tall. The duration of their vegetation was 182–189 days. The optimal period for the growth of the ground mass of plants fell on July-August. During this period, the leaves were quickly formed, the number of which was 28.8 ± 6.68 on the shoot. The correlation between the rate of accumulation of effective temperatures and the rate of regrowth of plant shoots was recorded.