Assessment of ornamental traits of japanese spirea (Spiraea japonica L.) cultivars when growing in the Moscow region

The aim of research is to study the phenological and morphological features, as well as a comprehensive assessment of the ornamental value of S. japonica varieties in the Moscow Region. The studies were conducted on the territory of the Leskovo perennial plant nursery (Egoryevsky District, Moscow Region) in 2022-2023. Air temperature and precipitation during the years of research in the region were below the long-term average values. The objects of research were Japanese spirea (Spiraea japonica L.) plants represented by 5 varieties: ‘Golden Princess’, ‘Goldflame’, ‘Hubert Gold’, ‘Pink and Gold’, ‘Superstar’. The varieties ‘Superstar’ and ‘Goldflame’ have the longest flowering period (50-60 days) - until early August. The onset of leaf color change in all studied varieties was observed in the first ten days of September, except for the ‘Superstar’ variety (10 days later). The varieties ‘Pink and Gold’ and ‘Superstar’ have the largest bush diameter (1.16-1.2 m). The variety ‘Golden Princess’ was characterized by the largest number of flowers (317 pcs/plant) and the greatest compactness of habitus (internode length - 0.83 cm). A scale of complex assessment of ornamental quality for summer-flowering spireas has been developed based on a number of features (plant shape, bush compactness, crown density, bark color, leaf blade shape and its edge, flower color, autumn leaf color). The ‘Pink and Gold’ variety had the greatest ornamental effect (83 points) due to the beautiful shape of the leaf blade, openwork crown and noticeable aroma. Recommendations are given on possible areas of use of the studied S. japonica varieties.