Changes in phenology induced by climate change occur across the globe with important
implications for ecosystem functioning and services, species performance and trophic
interactions. Much of the work on phenology, especially leaf out and flowering, has been
conducted on woody plant species. Less is known about the responses in phenology of
herbaceous species induced by global change even though they represent a large and important
part of biodiversity worldwide. A globally co-ordinated research effort is needed in order to
understand the drivers and implications of such changes and to predict effects of global change
on plant species phenology and related ecosystem processes.

Here, we present the rationale of the PhenObs initiative – botanical gardens as a global
phenological observation network. The initiative aims to collect data on plant phenology in botanical gardens which will be used alongside information on plant traits and site conditions to
answer questions related to the consequences of global change:

A. What is the variation in plant phenology in herbaceous species across the growing season
and in response to changes in climate?
B. How can plant phenology be predicted from species’ trait composition, provenance,
position and extent of the distribution range and species’ phylogeny?
C. What are the implications of this variation with respect to species performance and
assembly, biotic interactions (e.g. plant-pollinator interactions) as well as ecosystem
processes and services under changing land-use and climate?