Phenological Periodicity in Groups of Garden Plants in Spring Vis-a-Vis Their Ornamental Use

Knowledge of the phenological variability of plants is elementary for their more sophisticated use, especially for their use in groups and time. In an experiment with a model group of 76 garden shrubs we thoroughly followed and evaluated phenophases involving leaf and flower development. At the same time, we observed identical or analogous phenological events simultaneously occurring in sets of plants, trying to verify the existence of annual "vegetation waves" or, more precisely, the existence of certain phenological groups. The experiment was conducted in very early and early spring over a period of six calendar years. While studying these phenological phenomena, we discussed the impact of environmental factors and temperature values on the onset of phenophases, their dynamics, and how these factors affect cyclic, time-specific repeatability. The results confirm decisive influence of minimum air temperatures, notably of their dynamic distribution in time. Based on evidence gathered we verified the existence of six phenological groups which we defined on the basis of flowering time and which characterize very early and early spring phenological periods from the point of view of plant use in landscaping. Furthermore, we defined three phenorhythmic groups on the basis of budding time. The results of our experiment prove that plants may be used and classified more effectively based on an approximate forecast of when a combination of joined attractive phenological phenomena will appear and of how long it will last.