The results of introductory testing of prospective species of Spiraea L. genus for planting greenery in steppe zone of Khakassia

The aim of the research was to study the species of the spiraea Spiraea L. collection in the arboretum of the Institute for Agrarian Problems of Khakassia to introduce new promising plants into landscape gardening. The results of long-term introductory tests of 17 species of the spiraea collection are presented. To study the plants, well-known methods of observing the growth and development of shrubs, determining winter resistance and prospects were used. The studies were conducted on local species of spiraea and those from other regions. The data on the origin of species, their height in the arboretum, age, and ecological characteristics are given. The rhythm of growth and development of the studied plants for the period 2010–2017 are considered in detail. The average dates of occurrence of the main phenological phases, quadratic deviations and the degree of variation were statistically calculated. It is found that the terms of the onset of the main phases of development varied little in the years of research. The greatest variability (11.0–16.0 %) is typical for spring plant development dates. The grade scales were used to determine one the winter resistance and the perspectives of the spiraea species. In addition, a reference score to assess the state of the plants was presented. As a result, it has been established that the species of the spiraea collection can be divided into three groups by the flowering period. The first group of early flowering plants (from May 11 to May 30) was the most numerous (59 %), in the second group (26 %), flowering occurs from May 31 to June 15, and in the third group plants bloom after June 16 (12 %). A high score of winter resistance was noted in 48 % of the species under consideration. 64.7 % of the studied plants are suitable for introduction into planting greenery in the steppe zone of Khakassia. They are characterized by I and II grades of prospectivity. These are species with wide natural areas of growth, such as: spiraea trichocarpous Spiraea lasiocarpa Kar. & Kir., spiraea of Sargent Spiraea sargentiana Rehd., spiraea lavender S. x syringaeflora Lem.; for the first time these species can be recommended for the landscape gardening of settlements in the pre-Abakan part of the steppe zone of Khakassia.