## 4 Discussion  
A green facade reaches its maximum potential when the plants that compose it have a compact, healthy appearance and develop properly. The general appearance of plants (shape, arrangement of the component parts, etc.) influences surface temperatures [17]. Thus, it was found that a higher density of foliage produces a localized cooling that leads to a lower temperature at the level of the facade [8]. In this regard, it has been proven that plants have different performances [18]. In an experiment conducted in the Scandinavian climate, several plant species were tested. A harmonious development and good quality of coverage were observed in the following species: _Achillea millefolia_, _Bergenia cordifolia_, _Dianthus deltoides_, _Molinia caerulea_, _Nepeta fassenii_, _Salvia nemorosa_, _Sesleria heuffieriana_, _Antennaria diola_, _Armeria martiima_, _Iberis sempervirens_, and _Pilosella aurantiaca_. These species showed a lower degree of coverage, but their healthy and compact appearance recommend them to be used in combination with species with better coverage [10]. In the current experiment, the best survival coefficient of 91.66% was recorded in the species _Festuca glauca_ and _Sedum acre_ 'Aurea'. At the opposite pole are the two species of _Carex_ that recorded values of 5.20% (_Carex testacea_) and 13.54% (_Carex ostimensis_). The very low survival percentages obtained by the _Carex species_ led to the abandonment of their \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Cardinal Orientation** & & **Total Length of** & **Length of** \\
**of the Facade** & **Number of** & **Floriferous Rods** & **Inflorescence** \\
**Experimental** & **Floriferous Rods** & **(cm)** & **(cm)** \\
**Scheme** & & & \\ \hline C1N & 4 & 19.68 & 7.055 \\ C1E & 6.66 & 20.98 & 7.50 \\ C1S & 7 & 16.98 & 6.07 \\ C1W & 6.4 & 19.80 & 6.728 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Flowering _Heuchera x hybrida_ ‘Fire Alarm’ 2020. Figure 18: Evolution of the number of leaves in _Heuchen x hybrida_ ‘Fire Alarm’, May–December 2020.  
monitoring in the presented system. _Sedum species_ had high survival percentages (between 69.79% and 91.66%) and a good start at the beginning of the growing season, but their subsequent evolution was unfavorable, which is why they were no longer of interest in the study of plant behavior in this system. With an initial grip of 50%, _Pachysandra terminalis_ also had a good start but over the summer the plants began to suffer and dry out. During this period, 39.60% of all plants that survived over the winter were lost. Consequently, this species was removed from the study. The small percentage of survival, the modest onset, and the general appearance of plants of _Polystichum aculeatum_ also eliminated this species from the experiment. In terms of visual quality and coverage, _Festuca glauca_, _Heuchera x hybrida '_Fire Alarm' and _Heuchera x hybrida '_Marmalade' were favorably noticed. _Festuca glauca_ demonstrated a favorable development ensuring decoration throughout the year on the whole experimental scheme. However, on the southern facade, the development of _Festuca glauca_ plants was more modest, registering the majority of losses during the year on this part. During the entire monitoring period, the hybrids of _Heuchera_ had a compact appearance, rich and healthy foliage, and easily covered the surface of the vertical system. The losses during the growing season were small compared with the other species studied. For the dataset collected from _Heuchera x hybrida '_Fire Alarm', their statistical analysis was carried out using the two-factor ANOVA. Thus, in terms of plant diameter, the calendar month significantly influences the diameter of the plant (\(p\) value \(<\) 0.05), though there is no significant difference between the average values of the diameter on the northern facades of the experimental units (\(p\) value \(>\) 0.05), that is, the cardinal orientation did not influence this parameter.