Seasonal development rhythm of representatives of the genus <i>Spiraea</i> L. during introduction in the European North-East of Russia (Komi Republic)

Abstract

Shrubs of the genus Spiraea L. are distinguished by a great variety of ornamental features, but are still underused in ornamental horticulture in the northern territories. The issues of passing the seasonal cycle of plants under new harsh climatic conditions remain fragmentarily studied. The research was aimed at examining the features and identifying patterns of the seasonal rhythm of introduced species of the genus Spiraea L. The research was carried out on the basis of the collection of the Botanical Garden of the Institute of Biology, located in the middle taiga subzone of Komi Republic. Plants to be observed included nine species of three taxonomic sections of the genus Spiraea L. The long-term averages of phenological phases and periods of seasonal rhythm of species, as well as variability of features based on the results of phenological observations for six years in the period 2013-2018 were determined. The vegetation period of plants under new conditions lasts up to 145 days and corresponds to the vegetation period of the introduction station. Shoot growth lasts from 65 to 80 days in different species. The sequence of flowering, differences in the dates of onset and duration of flowering in different Spiraea species of three sections were noted. The duration of the prefloral period ranges from 18 to 41 %, the flowering period – from 8 to 31 % of the total vegetation period of plants. The total duration of flowering of the studied species accounts for almost 100 days. The least variability is specific for the period of vegetation of species (variability index up to 5.9 %), the greatest variability – for the period of flowering of plants (variability – up to 26.7 %). The taxonomic factor (85-91 %) was revealed to influence the passage of the generative phases of the seasonal cycle. The correlation interaction was determined between the main phenophases and the early leaf fall phase. The seasonal type of growth and phenological development of Spiraea plants is characterized by an early beginning and end of vegetation, a relatively short period of growth of shoots, and the consistency of average phenological dates. This phenorhythm of the studied species of the genus Spiraea demonstrates their potential for ornamental gardening in the northern region.