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.


Introduction
Knowledge of the phenology of wild and cultivated plants is important for horticultural crop production, meteorological sciences, and botany [1,2]. Plant phenology is a source of knowledge of periodic biological events affected by the environment and also the most reliable bioindicator [3,4]. It reflects biological and physical systems independently [5]. Changes in springtime phenological events of perennial [6][7][8] and woody plants have often been documented [3,5,7,9] and are more consistent in direction and magnitude than changes in summer and autumn phenophases [4,5,7,9,10]. Zheng et al. [5] selected 11 phenophases in nine woody species, namely, bud expansion, bud burst, first flowering, 50% of full flowering, end of flowering, first leaf, 50% of full leaf expansion, beginning of leaf coloring, end of leaf coloring, beginning of leaf fall, and end of leaf fall [5]. The beginning dates of spring and summer phenophases advanced with time, while the start of autumn and winter phenophases became delayed. These changes were significantly correlated with temperature [5]. Changes in climate can affect bud dormancy and cold hardiness, which are critical adaptations for the survival of winter cold stress by perennial plants of the temperate zone, Vitis species among them [11]. Bud dormancy allows perennial and woody plants to survive the winter in temperate climates [12].
To examine the effects of climate change, botanical gardens make standard phenological observations of many plant taxa growing on their area limiting the number of factors that might alter long term changes [13]. Their behavior can provide insight into how species will respond in the wild in terms of, e.g., changes in flowering, leaf-out times, Plants 2021, 10, 457 3 of 24 greenery in the city is not to be questioned [21,28]. Moreover, most rose cultivars produce few or no seeds and are not expansive [21,25,28].
Historical roses were known and cultivated before World War II [28,[30][31][32][33]. They deserve special attention and should be used to revitalize historical properties and urban greeneries and maintain the biodiversity and heritage of garden plants more often [11,30,32,34].
Warsaw, Poland, is located in the Central European Mazovian Lowland [35]. Over 1000 taxa were gathered in the National Collection of Rose Cultivars in the Polish Academy of Sciences Botanical Garden-Center for Biological Diversity Conservation in Powsin. Among them, more than 200 taxa of different origin are historical roses. Maintaining collections of plants, including ornamental plants, is an important task for botanical gardens due to its contribution to the preservation of biodiversity. The gene pool of roses is in need of expansion-its currently narrow range may lead to so-called genetic erosion [36][37][38][39]. This research can help to encourage the maintenance of biodiversity of the genetic pool of old garden roses and to implement the provisions of the Convention on Biological Diversity (CBD) drawn up in Rio de Janeiro on 5 June 1992.
Recent changes in climate are worrisome [40,41], and their influence on cultivated ornamental plants, including historical cultivars, is little known. The aim of this study was to compare different rose cultivars with each other and to perform long-term monitoring of selected phenology events to gain a better understanding of the effect of regional climate change. The observations presented here were conducted in order to evaluate the response in phenology of different rose cultivars to temperature over a period of time (from 2000 to 2016) and the ornamental value and frost resistance of 15 rambler rose cultivars in changing climate conditions. Moreover, the interrelationships between the phenology stages were analyzed.

Place of Research
Warsaw, Poland, is located in the temperate zone, with mixed continental and oceanic climate influences. The Polish Academy of Sciences Botanical Garden-Center for Biological Diversity Conservation in Powsin (52.6 • N, 20.5 • E) is located in the Middle Vistula mesoregion, separated from the Warsaw Plain by a high fluvial terrace at the border of a post-glacial height. The surface is covered with eolic sand fields and, in some areas, with dunes and partially with dust deposits created by periglacial and eolic processes [35]. Warsaw is classified as belonging to the USDA zone 6B with a minimal average temperature between −20.6 and −17.8 • C [22].

Weather Conditions
The average monthly temperatures in the years 1970-2016 measured in the Warsaw-Okęcie meteorological station (10 km in a straight line from PAS Botanical Garden) are shown in Figure 1 and expose the climate warming of the Warsaw region.
The weather conditions were observed in the years 2000-2016 in the PAS Botanical Garden CBDC in Powsin. The end of the 20th century experienced many extreme climate events, such as significant warm and dry periods in spring and summer and catastrophic rainfalls [41,42]. Especially adverse weather conditions for roses occurred in autumnwinter-spring (2002/2003, 2005/2006

Plant Material
The observations were conducted in the National Collection of Rose Cultivars of the Polish Academy of Sciences Botanical Garden-Center for Biological Diversity

Plant Material
The observations were conducted in the National Collection of Rose Cultivars of the Polish Academy of Sciences Botanical Garden-Center for Biological Diversity

Plant Material
The observations were conducted in the National Collection of Rose Cultivars of the Polish Academy of Sciences Botanical Garden-Center for Biological Diversity Conservation in Powsin. The shrubs of 15 once-blooming cultivars of different origin and belonging to different groups [21,25,28] were selected for this study (Table 1). One-year shrubs budded on rootstocks (Rosa canina L.) were planted in this period in a space that provided them with appropriate growth conditions, ample sunlight, supports, and soil enriched with organic materials with a pH of 6-6.5. Agrotechnical procedures were carried out according to the current technology [21,25,28]. The shrubs were fertilized with organic granular manure (50-60 g/pro plant) and the organic fertilizer "Azofoska" (4-6 kg/m 2 ; "Grupa INCO", Poland) every year in the spring after pruning. The roses were not irrigated from the second year after planting onward. The bases of shrubs were hilled up with bark for winter, and 2-3 protective sprayings of the plants against pests and fungal diseases were carried out every year. The shrubs were pruned every year, first in spring and then once more in the summer after overblooming [25].

The Evaluation of Plants
The roses were evaluated every year between 2000 and 2016. Every spring, damage caused by frost was recorded according to the following scale: 0-undamaged plants; 1-darkened vascular bundles on shoots, but buds still develop; 2-frost-damaged leaf-buds; 3-frost-damaged one-year-old shoot tips; 4-frost-damaged one-year-old shoots or only their living bases; 5-frost-damaged also 2-year-old and older shoots; 6-the shoots frost-damaged to the ground level; 7-complete plant frost damage (no signs of regeneration).
The plants' developmental cycle is subdivided into clearly recognizable longer-lasting principal growth stages described using numbers from 0-9 in ascending order. Certain stages may be shifted or omitted in some species [2]. The BBCH-scale is a system for the uniform coding of phenologically similar growth stages of plant species. The BBCH is an abbreviation of Biologische Bundesanstalt, Bundesortenamt, and CHemische Industrie [2]. The work of Meier et al. [1] described the principal phenological stages of wild and cultivated roses, also in relation to the production system [1]. The same scale was used in this research.
During the winter, early spring, and summer periods, observations of vegetative bud break and flowering were made and recorded twice a week (every 3-4 days). The first stages (07 and 11 BBCH) were observed on the middle part of uncut one-year shoots if these were not frost-damaged. It should be noted that after low cutting the development of buds was delayed and noted on the remaining shoots. The flowers present on the middle part of typical one-year mature shoots and the timing of their appearance were noted once they represented a stage in which the large majority of the flowers were flowering according the BBCH scale.
All the chosen phenology stages of observation of rambler roses were conducted using the BBCH-scale (Biologische Bundesortenamt, CHemische Industrie) described for rose cultivars [1]  The plants' developmental cycle is subdivided into clearly recognizable longer-lasting principal growth stages described using numbers from 0-9 in ascending order. Certain stages may be shifted or omitted in some species [2]. The BBCH-scale is a system for the uniform coding of phenologically similar growth stages of plant species. The BBCH is an abbreviation of Biologische Bundesanstalt, Bundesortenamt, and CHemische Industrie [2]. The work of Meier et al. [1] described the principal phenological stages of wild and cultivated roses, also in relation to the production system [1]. The same scale was used in this research.
During the winter, early spring, and summer periods, observations of vegetative bud break and flowering were made and recorded twice a week (every 3-4 days). The first stages (07 and 11 BBCH) were observed on the middle part of uncut one-year shoots if these were not frost-damaged. It should be noted that after low cutting the development of buds was delayed and noted on the remaining shoots. The flowers present on the middle part of typical one-year mature shoots and the timing of their appearance were noted once they represented a stage in which the large majority of the flowers were flowering according the BBCH scale.
All the chosen phenology stages of observation of rambler roses were conducted using the BBCH-scale (Biologische Bundesortenamt, CHemische Industrie) described for rose cultivars [1]   Although the bud breaking process involves several stages up until full leaf development [1,2], and despite the one-year shoots being a few meters long, only the initial points of breaking bud dormancy were recorded and considered in this work. For the above reasons, the following time intervals have been determined and are used in the paper in Figures 6 and 7  The timings of flowering entered into each recorded phenological stage were converted to the number of days since the 25th May. The resulting timing represents an average recorded from each exemplar of the evaluated cultivar. Although the bud breaking process involves several stages up until full leaf development [1,2], and despite the one-year shoots being a few meters long, only the initial points of breaking bud dormancy were recorded and considered in this work. For the above reasons, the following time intervals have been determined and are used in the paper in 0-lack of flowers; 1-some inflorescences on shoots; 2-no more than 5 inflorescences on 1 m of shoot, poorly flowering; 3-inflorescences with numerous flowers, flowering with average abundance; 4-more than 5 inflorescences on 1 m of shoot, the flowering plentiful and long; 5-exceptionally plentiful and long flowering with flowers densely covering the plant. The height of the plants was noted in spring after pruning and at the end of the vegetation season. It should be noted that the height of plants was not equal to the length of their shoots. The height of supports is given in Table 1.

Statistical Analysis
The results of frost damages, bud break (BBCH 07), leaf development (BBCH 11), the date of the start of flowering, and its abundance were analyzed by using an analysis of variance (one-way ANOVA), and Duncan's honest significant difference test was used to determine the significance of differences between the means (p ≤ 0.05). Additionally, Pearson correlations analyses between frost damages, bud break (BBCH 07), leaf development (BBCH 11), the date of the start of flowering, and its abundance were performed for the all cultivars. SPSS (IBM Statistics) software was used.
Moreover, the correlations were examined for each month from October to April, in selected seasons (2005/2006, 2009/2010, and 2015/2016) with long and frosty autumnwinter-spring periods, between average monthly temperature and:
Periods when the buds on unpruned shoots are at the beginning of breaking and the first green leaf tips are visible (BBCH 07); 3.
The bud on unpruned shoots are beginning to break, the first green leaf tips are visible, the first leaf pair has unfolded, not yet at full size, leaves are light green and/or bronze (BBCH 11); 4.
Additionally, the correlations between minimum air temperatures throughout the month and frost damage were examined. All years of observation were analyzed (2000-2016) [43].

Frost Damages
The frost damage of rambler roses is shown in Figure 5. Among the 15 varieties, only the shrubs of "Polstjårnan" did not have any damage every year. Moreover, "Lykkefund" and "Semiplena" had their one-year-old shoots or living bases frozen (5) only in the season 2009/2010 (the lowest minimal temperature was noted on 27.01. at −25 • C and 19.12. at −18.9 • C). "Kew Rambler" was also characterized by high resistance to frost-only one-year shoot tips were damaged. Lowered frost resistance was shown by "Rose Mary Viaud" and "Turner's Crimson Rambler". None of the cultivars experienced frost damage in the years 2007, 2008, and 2014 ( Figure 5).
Correlation analysis of the Ramblers in terms of frost damage showed a strict relationship between the average monthly temperature and the scale of frost damage in all cultivars.
Lower average temperature in October, January, and February was correlated with high frost damage in most cultivars, with the exception of "Polstjårnan" and "Lykkefund". Higher average temperature in November was correlated with high frost damage for the "Kew Rambler" and "Semiplena", while in March with seven cultivars (Table 2). Low minimum temperature was significant only in December and March (Table 3). Correlation analysis of the Ramblers in terms of frost damage showed a strict relationship between the average monthly temperature and the scale of frost damage in all cultivars.
Lower average temperature in October, January, and February was correlated with high frost damage in most cultivars, with the exception of "Polstjårnan" and "Lykkefund". Higher average temperature in November was correlated with high frost damage for the "Kew Rambler" and "Semiplena", while in March with seven cultivars ( Table 2). Low minimum temperature was significant only in December and March (Table  3).    . Frost damage of rambler roses according to the following scale: 0-undamaged plants; 1-darkened vascular bundles on shoots, but buds still develop; 2-frost-damaged leaf-buds; 3-frost-damaged one-year-old shoot tips; 4-frostdamaged one-year-old shoots or only their living bases; 5-frost-damaged also 2-year-old and older shoots; 6-shoots frost-damaged to the ground level; 7-complete plant frost damage (no signs of regeneration). Different letters indicate significant differences between cultivars and years. The Duncan's test (α = 0.05) was used.

Bud Breaking and Leaf Development
The most noteworthy differences in first phenological phases connected with bud break and leaf development were observed for "American Pillar", "Lykkefund", "Polstjårnan", and "Semiplena".
Most roses began their bud break after 11 April ( Figure 6). However, bud break occurred earlier in the last 3 seasons (2013/2014, 2014/2015, and 2015/2016) after mild winters and warm months of March and April. A similar observation was made in 2009/2010 with its warm March and April, in contrast to 2012/2013, with its long winter, frost and snow from December to March, and late but rapid spring in April with temperatures exceeding 25 • C. Bud break was observed the earliest in "Paul's Himalayan Musk", then "Kew Rambler", "Lykkefund", "Semiplena", "Polstjårnan", and occurred the latest in "American Pillar", "Bleu Magenta", and "Turner's Crimson Rambler" (Figure 6). climbing roses were similar in the following years (2000-2006 and 2008-2012), and also the determinants of this phenological phase rarely appeared before the 10th of April. An exception was observed in 2007, when leaves appeared on the roses excluding "Bleu Magenta", "Excelsa", "Maria Lisa", "Turner's Crimson Rambler", before April 10th, the winter was mild, and the average temperature in March was high (8.1 °C) in relation to other years. This phenological phase also appeared earlier by one or two points in the scale in the years 2014-2016 (Figure 7).   The first leaf pair unfolded about 10-14 days after bud break every year for most varieties (Figure 7). The earliest first leaf pairs to unfold were observed in "Lykkefund", "Paul's Himalayan Musk", and "Polstjårnan". "Semiplena", "Turner's Crimson Rambler", and "Veilchenblau" developed their leaves last. The stages of leaf unfolding in climbing roses were similar in the following years (2000-2006 and 2008-2012), and also the determinants of this phenological phase rarely appeared before the 10th of April. An exception was observed in 2007, when leaves appeared on the roses excluding "Bleu Magenta", "Excelsa", "Maria Lisa", "Turner's Crimson Rambler", before April 10th, the winter was mild, and the average temperature in March was high (8.1 • C) in relation to other years. This phenological phase also appeared earlier by one or two points in the scale in the years 2014-2016 (Figure 7).
Correlation analysis of the rambler roses for the timing of bud break and leaf folding showed a strict relationship with the average monthly temperature in all cultivars. The decrease of average temperature correlated with late bud break and the early leaf development stage (Tables 4 and 5 Correlation analysis of the rambler roses for the timing of bud break and leaf folding showed a strict relationship with the average monthly temperature in all cultivars. The decrease of average temperature correlated with late bud break and the early leaf development stage (Tables 4 and 5 Table 4; Table 5).

Flowering
The rambler roses started flowering in the first days of June. "Maria Lisa", "Paul's Himalayan Musk", and "Polstjårnan" were the first to start blooming; "Excelsa" and "Rose Mary Viaud" were the last ( Figure S4). If the shoots were damaged to the ground (points 6 and 7 on the scale), the low pruned shrubs did not flower, or only a few flowers appeared on old parts of shoots. Exceptionally plentiful and long flowering was observed in "Semiplena" and "Kew Rambler", "Lykkefund", "Paul's Himalayan Musk", and "Polstjårnan". Low quality of flowering, especially after frosty winters, were noticed in "Bleu Magenta", "American Pillar", "Belle de Baltimore", "Maria Lisa", and "Rose Mary Viaud". Moreover, the flowering was exceptionally plentiful after mild winters (2007, 2008, and 2014−2016) in all plants that were already a few years old (Figure 8).
Correlation analysis of the ramblers for the timing of the start of flowering showed a strict relationship between the average temperature in winter and spring months for all cultivars. A decrease in the average temperature in March correlated with a later start to flowering in "American Pillar", "Belle de Baltimore", "Excelsa", "Polstjårnan", and "Raubritter", while a decrease in the average temperature in April was connected with a later start to the flowering of "Kew Rambler" and "Veilchenblau" (Table 6). Correlation analysis of the ramblers for the timing of the start of flowering showed a strict relationship between the average temperature in winter and spring months for all cultivars. A decrease in the average temperature in March correlated with a later start to flowering in "American Pillar", "Belle de Baltimore", "Excelsa", "Polstjårnan", and "Raubritter", while a decrease in the average temperature in April was connected with a later start to the flowering of "Kew Rambler" and "Veilchenblau" (Table 6).

The Correlation between Frost Damage, Early Phenology Stages, and an Abundance of Flowering
The correlation analysis of the rambler roses for all cultivars showed a strict relationship between frost damage, early phenology stages, the timing of the beginning of flowering, and its abundance (Tables 7-9). Generally, high frost resistance, a late beginning to the flowering period but with early bud breaking and leaf folding correlated positively with plentiful abundance of flowering. The plants with lower frost resistance ( Figure 6) showed a tendency to start bud breaking and leaf development later. These included "American Pillar", "Belle de Baltimore", "Bleu Magenta", "Excelsa", "Kew Rambler", "Maria Lisa", "Paul's Himalayan Musk", "Raubritter", "Rose Mary Viaud", "Turner's Crimson Rambler", "Veilchenblau", and "Wartburg" (Tables 8 and 9). Table 7. Correlation matrices between frost damage, early phenology stages, beginning of flowering, and its abundance in rambler roses for all cultivars taken together.

Discussion
Changes in the phenology of woody plants [5], roses [9], and crops [40,41] were observed to accompany temporal changes in average temperature and sometimes other weather variables [7]. The difference attributed to changes in atmospheric circulation contributed to the acceleration of several spring phenophases during the years 1951-1998, although these changes were generally greater in Western Europe than in Central or Eastern Europe [44]. This research throughout the years has shown that changes in phenology and overwintering seem to be the effect of climate change resulting from global warming [5,44,45]. This can be easily observed by comparing the plant hardiness zone map published by Heinze and Schreiber in 1984 [46] and the current Plant Map [22]. This tendency was noticed in PAS Botanical Garden CBDC in Powsin (Figure 2, Figures S1 and S3) and Okęcie station (Figure 1). In the research of Zheng et al. [5] most spring and summer phenophases occurred earlier and most autumn and winter phenophases in observed woody species occurred later between 2003 and 2012 than between 1987 and 1996 [5].
The most important criterion that decides on the success of a rose's cultivation and its ornamental value in a given place is the ability of the shrubs to survive the winter without any influence on their further growth and blooming in present and following seasons. Milder winters in Poland allow for the cultivation of a wider range of plants, some of which would have had no chance of survival even 20-30 years ago [19]. Rambler roses are considered insufficiently resistant to frost and require covering in the Polish climate [21,28]. Similarly to the observed ramblers, many other species, historical groups, and cultivars of roses bloom once per year and start flowering on one-year shoots and older [9], e.g., Spinosissima [47] and Gallica-Hybrids [31]. However, frost damage to the shoots of rambler roses has always resulted in them completely dying out, with visible earlier darkened vascular bundles on shoots or with darkening buds. The shoots, which were initially assessed on a scale of 1 or 2, died out in May. Figure 5 provides the final effect of shoot damage noted in late spring and Table 10 the height that required pruning. The intensely growing shrubs quickly regenerated (Table 10), but nevertheless the pruning reduced blooming in the given year ( Figure S4 and Figure 8). However, all varieties, excluding "Bleu Magenta", flowered in every season between 2011 and 2016, and the last three years were plentiful in flowers (Figure 8). In the research of Pihlajaniemi et al. [15], the differences in winter hardiness between five old shrub varieties of roses were all statistically significant within five sites of observations in North Finland in 1993-1999 [9].
The flowers are a fundamental part of the ornamental value of roses. Overwintering in once-blooming ramblers is especially significant because of their manner of flowering. Flowering was limited, or the shrubs did not bloom at all, in years that followed severe winters (Figures S1 and S4 and Figure 8, Tables 7-9), when the shoots were shortened close to the ground or down to the ground itself (at 6-7 on the scale of frost-damage), especially for young shrubs (Table 10). More shoots remained after pruning shrubs that were already a few years old if the frost damage was less than 5 in scale ( Figure 5). The flowering would begin a few days later, and the abundance of flowering was always lower in scale in years after substantial winter damage and necessary low pruning, and a few days earlier in years following mild winters and early springs (Figure 8 and Figure S4). Both the longer growing season and higher total monthly temperature in March could be reasons for earlier flowering (Tables 7-9). The duration of flowering of Rugosa, Gallica, and Spinosissima in the PAS Botanical Garden in the years 2000-2012 was similar [31,33,47,48]. Additionally, in the research of Pihlajaniemi et al. [9] differences in the ornamental appearance of flowering were statistically significant in the case of six old rose genotypes studied across six years within five sites of observation in North Finland. The mentioned shrub roses are highly frost resistant [9] in comparison to ramblers.
The results of long-term observation also suggest wide adaptability of the observed varieties to the changing and warming climate in the Mazovian Lowland. Warming experiments fail to account for the full magnitude of observed changes in phenology, which suggests that other factors may play important roles here [7]. In the case of this experiment, such factors could include the age and origin of the shrubs. The most studied ramblers originate from Asia, which suggests they may have a lower resistance to frost [25,28]. "Lykkefund" and "Polstjårnan" are highly resistant and did not experience frost damage every year, in contrast to most varieties from the Alba group, e.g., "Celestial", "Hurdals", "Maiden's Blush" [32], Gallica [31], Spinosissima [47], and most old and modern cultivars of Rugosa-Hybrids [33,48], which were all observed in the same climate conditions in the PAS Botanical Garden. It was noted that shrubs of rambler roses that were older in age had a higher tolerance for frost and unfavorable climate conditions than younger specimens, which was also visible at the flowering stage. The warming climate enables the cultivation of less frost resistant plants, however they should nevertheless be protected in the first years of cultivation. It is possible that in the coming years they will be able to survive without protection in microhabitats with suitable conditions [19]. The weather in autumn-winter-spring seasons in the years 2000-2016 was changeable with a tendency for minimal, average, and maximal temperature to increase (Figures S1-S3).
There is only perfunctory information available in the literature on the phenological phases, timing, or duration of the flowering period of old rose cultivars. Throughout the long period of this research, the climate conditions were changing. The timings of phenological phases were different depending on the origin of ramblers but also strictly connected to weather conditions. Similar correlations were observed in other closely connected groups of cultivars, e.g., Spinosissima [47], Rugosa [33,48], Gallica-Hybrids [31], and old shrub genotypes of roses [9]. This relationship was especially relevant in the first phenological phase (BBCH 0) connected with bud break and leaf development (BBCH 1) and with the timing of initial flowering [31,33,47,48]. The results are in line with the view that in temperate climates the timing of phenological phases is particularly dependent on the combination of temperature values [9,20] and photoperiodic courses [49]. Bud break occurred earlier with every next year, except for after frosty winters, when it would take place later. Bud break appeared around a dozen days earlier in later years, especially in 2014-2016, which could be caused by a longer growing season. As Krużel et al. [50] [50]. These results are compatible with those of [7], which showed that spring events such as leafing and flowering typically advanced by a median of 4-5 days per degree Celsius [7]. In Poland, accelerated bud break and leaf development after a warmer winter typically exposes the young shoots of rambler roses to night-time spring frost in mid-April and early-May [50,51]. Moreover, research on Vitis species showed that changes in phenology caused by climate change could disturb the process of cold hardiness [11]. This process requires dormancy induction in the early winter and is responsible for the maintenance of a dormant state throughout the season, which is crucial to the plants' survival [11,12].
Moreover, autumn events such as leaf coloring or leaf fall have usually become delayed [7] due to the prolonged growing season [50]. The height of rambler rose shrubs was determined to a large extent by supports, although shrubs of most of the observed cultivars reached their maximum height in autumn independently of the height of spring pruning. The prolonged growing season [50] and growth processes [51] also in rambler roses could disturb the process of hardening before winter dormancy-a period that they require woody plants of the temperate zone [12].

Conclusions
Ramblers can be cultivated and grow tall in the warmer western parts of Europe, where, because of mild winters, they flower reliably every year [25]. The results confirm that changes in thermal characteristics of the climate of Poland and the associated extension of the meteorological growing season [50,51] and growth season [51] have enabled the introduction of thermophilic plants with higher thermal requirements in cultivation [19,50,51].
Many-year observations of ramblers showed their favorable adaptation to the climate in Poland and the possibility of their wider use in regions with a hitherto cooler climate. However, they have also shown a differentiation in the tolerance of different varieties not only due to frost in winter but also changes in temperature in spring and autumn. These factors had an important influence on the scale of frost damage, growth, and flowering of roses. The average air temperature in autumn-winter-spring correlated strictly with the roses' early phenological phases.
Rambler roses are a valuable supplement to the available assortment of vines, especially for city greening. Recent years of mild winters and low maintenance made the studied ramblers more useful for a wide range of applications as ornamental plants in parks and rendered them especially preferable for historical garden layout cultivation. This is particularly significant in Central and Eastern Europe, including Poland, where many historical gardens are in poor condition [34].
Currently, rambler roses are not the subject of wide cultivation research, but due to their ornamental merits, which were appreciated in the past, it is worth considering the possibilities for re-establishing their significance. The maintenance of old cultivars, including roses, in cultivation is dependent mostly on resistance to climate conditions.