The science that treats the periodic biological phenomena with relation to climate, especially seasonal changes. Phenological events are stages of plant growth. From a climatological viewpoint, these phenomena serve as bases for the interpretation of progress in local seasons and the climatic zones, and are considered to integrate the effects of a number of bioclimatic factors on rate of plant development. Phenology may be considered a branch of the science of bioclimatics, the sequence of plant or crop development stages through its life cycle. Growth stages may be defined by stage of physiological development such as germination, first true leaf, flowering, maturity, etc., and/or by physical stage such as planting, emergence, harvest, etc.