## 4 Discussion  
Phenological observations of plants are useful for the examination of climate change, but cultivated ornamentals are rarely taken into consideration. The most interesting features are frost damage, flowering abundance, and the timing of flowering. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Variable** & **Bud Break** & **Leaf Development** & **Frost Damage** & **Beginning of** & **Abundance of** \\  & & & & & \\ \hline ‘Paul Scarlet Climber’ & & & & & \\ \hline Leaf Development & 0.716 *** & 1.000 & & & \\ Frost Damage & 0.355 ** & 0.735 *** & 1.000 & & \\ Beginning of Flowering & 0.395 ** & \(-\)0.444 ** & 0.386 ** & 1.000 & \\ Abundance of Flowering & \(-\)0.321 ** & 0.525 ** & \(-\)0.613 *** & \(-\)0.225 * & 1.000 \\ \hline ‘Venusta Pendula’ & & & & & \\ \hline Leaf Development & 0.847 *** & 1.000 & & & \\ Frost Damage & 0.635 ** & 0.882 *** & 1.000 & & \\ Beginning of Flowering & 0.103 ** & 0.200 * & 0.325 ** & 1.000 & \\ Abundance of Flowering & \(-\)0.816 *** & \(-\)0.881 *** & \(-\)0.920 *** & \(-\)0.146 * & 1.000 \\ \hline ‘Eöphrine Drouhin’ & & & & & \\ \hline Leaf Development & 0.823 *** & 1.000 & & & \\ Frost Damage & 0.394 ** & 0.660 *** & 1.000 & & \\ Beginning of Flowering & 0.591 ** & 0.537 ** & 0.335 ** & 1.000 & \\ Abundance of Flowering & \(-\)0.560 ** & \(-\)0.391 ** & \(-\)0.298 * & \(-\)0.295 * & 1.000 \\ \hline \multicolumn{5}{l}{Note: The correlations are significant at \(\alpha\) = 0.01; marked: * 0.100–0.299—low; ** 0.300–0.499 –restrained; *** 0.500–0.699—high; *** 0.700–0.899—very high; *** \(\geq\)0.900—almost full.} \\ \multicolumn{5}{l}{values: ns—not significant.} \\ \end{tabular}
\end{table} 
Table 13: Correlations matrices between frost damage, early phenology stages, and beginning and abundance of flowering in climber roses: ‘Paul Scarlet Climber’, ‘Venusta Pendula’, and ‘Zéphirine Drouhin’. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
The most important factors limiting the cultivation of plants are frost resistance [38; 41] and the ability to grow in changeable climate [25; 45; 53]. A significant additional criterion for the use of species as ornamental plants is their ornamental potential and value [54]. The basic value of climber roses is growth and flowering abundance in present and following seasons [45; 55; 56]. Most taxa of historical climber roses flower on one-year-old and older shoots [1; 2; 38], which could limit their ornamental value in adverse climatic conditions during which rose shoots freeze. The once-blooming climber rose cultivars presented in this research flower on 2-year-old and older shoots, and their ornamental value is limited particularly by frost damage. This research showed that autumn-winter-spring conditions determined their over-wintering and consequently the frost damage to shoots (Tables 3 and 4, Figure 5) as well as the necessary height of pruning (Figure 6). Frost damage has a dominant role not only in terms of the period of flowering and its abundance, but also on the period of bud break and leaf development (Tables 11-13). The observation in Poland showed the lengthening of the growing season by a few days [50]. However, as indicated the research of [52], the number of the days with minimum temperature below 0 \({}^{\circ}\)C may increase. This suggests that earlier terms of early phenological events (starting of bud break, leaf unfolding) in roses could lead, in the future, to shoot damage by spring frost causing a lack of flowering or low abundance. The studied varieties originated in Asia and were grown in a warmer climate with milder winters [1; 2], which suggests insufficient resistance to negative temperature. The many years of observation of growth and flowering of chosen groups of rose cultivars were conducted in the PAS Botanical Garden CBDC in Powsin [38; 39; 40; 41; 42; 43; 44]. The climber roses observed in this research had different responses to winter conditions depending on their origin.