Artificial light at night (ALAN) is a rapidly expanding form of pollution that alters natural light regimes and threatens biodiversity. While many studies have documented its effects on animal behaviour, the consequences for plants, and the ecological services they provide, remain underexplored. We investigated how ALAN modifies the timing and availability of floral resources in wild plant communities of central European agricultural landscapes. From 2022 to 2023, we conducted a large-scale field experiment in Swiss wildflower strips, exposing sites to LED streetlights to simulate ALAN (n = 14) while paired controls remained dark (n = 14). Using phenological monitoring and time-lapse photography, we quantified both daily and seasonal changes across multiple species. At the daily scale, ALAN altered flower opening and closing patterns, delaying petal closure in a night-flowering species and advancing morning opening in a day-flowering species. At the seasonal scale, ALAN advanced seedling emergence in half of the species studied (n = 6) and shifted flowering schedules in 75 % (n = 16). In some cases, flowering onset, progression, and peak bloom occurred more than 10 days earlier, while other species showed delayed flower disappearance. These shifts change when floral resources are available in the landscape, potentially exposing reproductive stages to suboptimal abiotic conditions and disrupting synchrony with pollinators and herbivores. Such desynchronization may reduce reproductive success, alter interaction networks, and cascade to affect community composition. Our findings demonstrate that ALAN alters the temporal dynamics of plant resources at both daily and seasonal scales, potentially disrupting ecosystem stability.