The seasonal development characteristics of different taxa and cultivars of rhododendrons in Northern Lithuania. 2. Flowering peculiarities.

The pattern of seasonal development of rhododendrons, as well as of all other introduced plants, in the conditions of a specific region is one of the most reliable indicators of their positive acclimatization. One of the most important indicators is the time and duration of the production of generative structures. The grouping of these plants into phenorhythmotypes made it possible to evaluate the indicators characterizing the flowering peculiarities of rhododendrons. We assessed flowering peculiarities of 37 deciduous and 89 evergreen or semi-evergreen taxa and cultivars of rhododendrons (1–7 individuals of each taxa and cultivars) that had reached the generative status of biological maturity, but a different calendar age. The rhododendrons grown in Northern Lithuania were grouped into specific phenorhythmotypes according to indicators of flowering beginning, flowering ending and average duration of flowering. According to indicators of flowering beginning and flowering ending, the rhododendrons were classified into phenorhythmotypes of 1) especially early, 2) early, 3) rather late, and 4) especially late. According to flowering duration, the rhododendrons were divided into phenorhythmotypes of 1) short flowering duration, 2) medium flowering duration and 3) long flowering duration. These results are relevant for grouping different types of rhododendrons intended for planting in green areas of urban territories.