The duration of the vegetation period – i.e. the time that elapses between leafing out (the emergence of the first leaf) in spring and the initiation of leaf loss in autumn – is a highly significant ecological parameter that has a considerable influence on both plant productivity and the biogeochemical cycling of vital nutrients in ecosystems. However, the mechanisms that determine the length of the vegetation period for any given species are poorly understood. Hence, in order to assess the potential impact of global climate change on plant productivity, for instance, more information on the timing of the growing seasons of a wide range of plant species is required. In a large-scale study, LMU botany professor Susanne Renner and her colleague Constantin Zohner have now measured this parameter for a large sample of woody plant species from the Northern hemisphere. Their findings, which have now been published in the journal Nature Ecology and Evolution, reveal significant differences between species that are native to North America on the one hand, and European and East Asian trees and shrubs on the other.