Фенологическая характеристика интродуцированных растений близкородственных видов рододендронов подрода Rhodorastrum (Maxim.) Drude (серия Daurica Pojark) в Ботаническом саду ИГУ

Abstract

An analysis of the seasonal development of rhododendrons of the Daurian series during introduction in the Irkutsk Botanical Garden was completed and their initial prospects for use in landscaping settlements in Baikal Siberia were assessed. For this purpose, regular phenological observations were carried out for the plants of these species since 2013. A comparative characteristic of the phenological development of four rhododendron species of the Daurian series was given. According to our observations, the processes of adaptation of introduced plants in Irkutsk conditions are primarily depending on the temperature conditions of autumn-winter-spring with a relatively favorable growing season. The most destructive factors for rhododendrons are high insolation at considerable minimum temperatures in winter, late autumn and early spring periods, also an absence of stable snow cover in late autumn and early spring, and sharp daily variations of air temperature. The hydrological regime is also not very favorable. The root layer of the soil is often subjected to severe dehydration at low air humidity during the growing season. This is very dangerous for rhododendrons with their shallow root system. The seasonal development of rhododendrons is greatly influenced by their winter hardiness, drought tolerance, thermal and hydrological regimes of the growing season, the duration of the frost-free period, and a certain value of the daily temperature amplitudes in spring and fall. The results of the analysis of long-term phenological observations of the development of introduced plants led to the following conclusion. Among the rhododendrons of Daurian series in the introduction in Irkutsk, Rhododendron ledebourii Pojark., Rhododendron dauricum L. and Rhododendron sichotense Pojark. have shown themselves promising without limitations. They are characterized by fast growth, abundant flowering, early entry into the generative phase. Also, an early and short period of growth processes and timely entry into a state of rest are characteristic of them. All this contributes to the successful maturation and hardening of shoots, due to which their winter hardiness is estimated at 1 point, less often at 2 points. Rhododendrons ledebourii and Rhododendron sichotense are the most decorative due to the regularity of flowering, the abundance of flowering and the size of the flower. Rhododendron mucronulatum Turcz. is recommended for use in landscaping settlements with milder climatic conditions or in settlements within its natural range.