Phenology, which is derived from the Greek words "phainesthai" meaning show or appear and "logos" meaning science, is the study of the seasonal timing of live cycles and how they respond to seasonal changes in their environment.

Plant phenology is timing the development stages (phenophases) of plants, such as bud burst, beginning of leaf unfolding, beginning of flowering, first ripe fruits, autumn colouring or leaf fall.

The timing of phenological phases depends on numerous environmental conditions: air temperature, precipitation, soil type, soil moisture and insolation. In mid- and high latitudes with dormancy (vegetation rest) in winter and active growing period in summer, air temperature has the greatest influence on phenology, especially for the spring phenological phases. Therefore, phenological observations are one of the most sensitive indicators of climate impacts on vegetation. For more informations see e.g.:

          Schwartz, M.D. (2003): Phenology: an integrative environmental
          science. Dordrecht: Kluwer.