The visible developmental stages of trees over the course of the year are an important indicator of their vitality. In addition, temporal changes in the occurrence of these developmental stages can be an indication of changing environmental conditions, e.g. with regard to climate change, the deposition of air pollutants or the dynamics of the mass occurrence of forest pests. At the same time, changes in phenology can also be used to draw conclusions about the adaptability of tree species, for example with regard to water utilisation, growth and regeneration capacity.