Analysis of varietal diversity, decorativeness and peculiarities of growth and development of cultivars Dahlia cultorum Thorsrud & Reisaeter in the collection of the biostationary of Bila Tserkva NAU

Abstract

Aim. In order to identify promising cultivars of Dahlia cultorum for use in landscaping in Kyiv region, the analysis of the system of qualitative and quantitative indicators of cultivars of dahlias, the peculiarities of their growth and development in the absence of irrigation is conducted. Methods. To analyze the diversity of Dahlia cultorum cultivars at the biostationary of Bila Tserkva NAU, the classification developed by the American Society of Dahlia (ADS classification) was used. The cultivar assortment of dahlias was studied according to the descriptions of the catalog of the company “SontseSad”, which transferred 108 cultivars of Dahlia cultorum to Bila Tserkva NAU biostationary in 2014. Phenological rhythms of growth and development of dahlias were studied according to the methods of B. K. Shybniev, H. D. Yurkevych, and D. S. Holod. The increment of dahlias was measured during the period of active growth, the size of the flower — during the period of its full opening with the help of a measuring ruler on 5 specimens of each cultivar every decade. Results. Based on the analysis of the varietal composition of Dahlia cultorum collection of dahlia cultivars of Bila Tserkva NAU biostationary, it was found that the largest number of 36% belongs to the cultivar group of decorative dahlias, 12% — to cactus, 7% — to spherical and 1% to pompoms and anemones. The mixed cultivar of dahlias is 43.4%, among them the most numerous group of dahlias with dissected leaves “Deer antlers” — 48%, “Karma” — 19%, pot — 12%, French collection — 21%. According to the color spectrum, the collection is dominated by dahlias of red color — 29%, pink — 19%, yellow and orange — 16% each, violet — 12%,  white color — 6%. Two-color cultivars amount to only 2%. Observations show that in May–June, due to the long and dry period and the lack of artificial irrigation, all cultivars of dahlias at Bila Tserkva NAU biostationary were marked by very slow growth. As of July 15, the height of dahlia bushes averaged 30–50 cm, which was significantly less than the size presented in the catalog of the magazine “SontseSad”. Conclusions. The collection of dahlias at Bila Tserkva NAU biostationary includes 108 cultivars belonging to seven main cultivar groups, including 11 cultivars from the new French collection. Early in the first decade of July, the cultivars ‘Islande’, ‘Maki’, ‘Sir Alf Ramsay’, ‘Mingus Alex’, ‘Glorie van Heemstede’ begin to bloom. Latest of all, in August, cultivars ‘Babylon Rose’, ‘Amanda’, ‘Aitara Bronwyn’, ’Karma Gold’, ‘Gallery Rembrandt’, ‘Lilac Time’, and ‘Star Spectacle’ began flowering. It is established that the period from the appearance of the bud to the opening of the flower in dahlia cultivars lasts 25-30 days. The first buds appeared in early July, but their peduncles were very short and such flowers were not suitable for cutting. In fact, the blooming central flower itself was 5-10 cm lower than the second-order buds around it, and therefore had a limited view from the inflorescence, which led to a loss of decorativeness in the cultivars ‘Romance’, ‘Candlelight’, and “Karma Bon Bini”. The duration of flowering of one dahlia flower in different cultivars ranged from 5 to 17 days. The longest period of blooming of one flower is 14-17 days in ‘Autumn Fairy’, ‘Nagano’, ‘Idylle’, ‘Babylon Brons’, ‘Duet’ cultivars. The shortest blooming period of one flower is 5-7 days for ‘Ellen Huston’, ‘Champs Elysees’, ‘ThykiYori No Shisha’, ‘Aspen’ cultivars. Due to the high air temperature and the long rainless period, the peak of flowering of dahlias in the conditions of  Bila Tserkva NAU biostationary was at the beginning of September.