Photoperiod–Temperature Interactions in a Changing Climate: A Review of Plant Phenological Responses

Aim: Climate change is reshaping plant phenology and species distributions, especially in temperate and boreal ecosystems, where advances in spring events have already extended the growing season. While temperature has been the primary focus of many studies, the role of photoperiod—a stable, latitude-dependent cue—remains underexplored. This review aims to assess the combined effect of both photoperiod and temperature on plant responses to climate change. Location: Northern hemisphere. Taxon: Spermatophytes. Methods: In this review, we synthesise evidence from 68 studies covering 344 taxa to evaluate how photoperiod interacts with rising temperatures to influence plant phenology. Results: Key life cycle events such as bud burst, flowering and senescence are shown to be shaped by complex photoperiod–temperature interactions. Spring phenology seems to be the most affected by this interaction, with long photoperiods counterbalancing insufficient winter chilling in many species. Moreover, photoperiod constraints may limit the adaptive potential of certain species, particularly in high-latitude regions, and act as a barrier to range expansion under climate warming. Conclusions: Understanding temperature–photoperiod interactions is essential for predicting species responses, guiding conservation strategies and improving ecosystem management in a changing climate. For example, this interaction might affect the choice of suitable plant material for assisted colonisation.