SORBUS ‘JOSEPH ROCK’ (ROSACEAE) IN SAINT-PETERSBURG
Abstract
The rowan "Joseph Rock" ( Sorbus 'Joseph Rock') is diploid with normal number of chromosomes (2n=34). This is a tree with pyramidal crown and bright red autumn color of leaves, it is absent in Russia. Since 2006 this species has been grown in the Peter the Great Botanical Garden of the Komarov Botanical Institute RAS (Saint-Petersburg, Russia). Here it has proved to be winter hardy, of the same winter hardiness as the local S. aucuparia L. and S. commixta Hedl. (supposed to be the hybrid of it). At the age of 12 years it has reached almost 5 m height. At the age of 10 years (in 2015), the first fruiting was observed. The purpose of the work is to determine the biometric parameters of fruits and to assess the quality of the seeds of the rowan "Joseph Rock" of its own reproduction. In each fruit (apple) the number of seeds varies from 1-2 to 4, rarely - to 5. The seeds of own reproduction in the crop of 2017 are characterized by good quality (the percentage of full-fledged seeds in different samples was from 22 to 64 %). Plump seeds correspond to the V and IV classes, pests of seeds are not found. The laboratory germination of seeds stratified from three to five months was 34-48 %. The field germination (when sowing in autumn in pots), after cold stratification, amounted to 25-33 %. In 2018 the seed reproduction were obtained for the first time. This is one of the most decorative rowans with rare yellow color of fruits. It is highly valued in the decorative gardening of Western Europe, and it is of interest for the greening of St. Petersburg.
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Published 2018-06-25