Response of Rambler Roses to Changing Climate Conditions in Urbanized Areas of the European Lowlands.

Climate change affects the possibility of crop production and yield and disrupting the maintenance of crop biodiversity, including ornamentals. Warsaw is located in a temperate zone with mixed continental and oceanic climate influences. This research examines the response of once-blooming rambler roses to changing climate conditions in connection with their frost resistance and ornamental value. The 15 selected rambler rose cultivars were observed in the years 2000-2016 in the Polish Academy of Sciences Botanical Garden-Center for Biological Diversity Conservation in Powsin. Damage to shrubs caused by frost, the timing of bud break, leaf development, and initial, full, and final flowering were recorded. We show that changes in phenology and frost damage were the effect of weather conditions in the autumn-winter-spring period. Frost damage influenced the flowering and growth of plants in different ways, depending on the extent of required pruning. The cultivars most highly tolerant to frost damage were: "Lykkefund", "Polstjårnan", and "Semiplena". During the final years (2014-2016), due to mild winters, all of the studied rose cultivars could be used for a wider range of applications than previously (2000-2006 and 2009-2013). Their reintroduction helped to maintain biodiversity of old cultivars, which makes these roses a proposal for the lowlands of Central Europe.