The abundance and composition of flowers within plant communities shape the resources available to flower-visiting insects. However, it remains unclear how nutrient enrichment and changes in grazing impact plant communities and their floral resources, and whether these effects contribute to ongoing pollinator decline. We investigated how the abundance, diversity, and species composition of flowers (excluding graminoids) respond to long-term nutrient additions and grazing exclusion in two high-latitude grasslands (tundra and montane). We used two factorial experimental designs: 1) a nutrient experiment with additions of nitrogen (N), phosphorus (P), and potassium (K with micronutrients, and 2) a grazing experiment that included combined NPK addition with and without grazing exclusion. Flower abundance was assessed in 5 × 5 m experimental plots after 6–10 years of treatments. N and P interactively affected flower abundance, with N counteracting the positive effects of P. N reduced flower abundance in the montane grassland, whereas P and K increased it. Grazing exclusion increased flower abundance, with its effect amplified under NPK addition, but this joint treatment reduced flower species richness. Grazing exclusion reduced flower species diversity, with contrasting site-specific effects depending on NPK. N, P, and K addition, as well as grazing exclusion and NPK addition, changed the composition of flower assemblages. At the montane grassland, joint NPK addition and grazing exclusion led to strong dominance of forbs, such as Anthriscus sylvestris and Geranium sylvaticum, and grazing exclusion led to homogenisation of the flower community at the montane grassland. Our study demonstrates the importance of grazing and nutrients as key determinants of floral resources, which are vital for flower-visiting insects. We suggest that quantifying floral resources could contribute to ecosystem status assessment. Our findings offer insights for managing and conserving pollinator habitats in the face of environmental change.