Creation of a collection fund and study of cultivars of daylilies in the M. M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine

Purpose. Analysis and comparative study of daylily cultivars from the collection fund of the M. M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine (NBG), selection of assortment for decorative horticulture and landscaping. Methods. Cultivars from the NBG daylily collection were studied. The cultivars were evaluated in terms of their aesthetic and economic attributes, and were classified according to their coloration and the timing of their flowering. The author of the cultivar, country of origin, year of creation and introduction into the NBG were also identified. The cultivars were also grouped according to these parameters. Results. The NBG daylily collection is the result of 40 years of introduction and 20 years of breeding work with this crop at the NBG. It includes 174 world cultivars, 26 cultivars of Ukrainian breeding and more than 1000 hybrid seedlings. Most of the cultivars (79) were introduced in 2000–2009. The main part of the current structure of the daylily collection consists of cultivars bred in the 1960–1970s. Most of these are hybrids from American breeders: David F. Hall (20 cultivars) and Allen Wild (46 cultivars). A total of 15 new cultivars were developed based on the original collection. These new cultivars feature double flowers, a valuable trait for hybrids in Ukraine. For effective use in ornamental horticulture and landscaping, the cultivars were grouped according to flower colour and flowering time. The yellow­flowered group is the most widely represented. A large number of cultivars with red flowers are inherent in hybrids bred between 1980 and 1999. Cultivars from modern breeding are mostly represented by the purple and pink colour group. Most of the cultivars in the collection are early and medium early. The smallest part is made up of medium­late and late hybrids. Conclusions. The modern daylily collection is representative. The cultivars introduced into the NBG illustrate the main stages of breeding work with the crop and the achievements of breeders from different countries of the world. The collection includes early and medium early, medium, medium late and late flowering cultivars. Varying in colour and flowering time, the collection can be effectively used to extend the flowering period of daylilies by three months (from the second decade of May to the second decade of August) in ornamental gardening in Ukraine and in various landscape compositions.