Apply Phosphorus-Rich Bloom Booster
Phosphorus is key for bud formation. A light application of bone meal or rock phosphate around rose bushes (Rosa spp., native to Europe and Asia, some species naturalize but rarely invasive) and other heavy bloomers ignites bud set without encouraging leafy overgrowth. I sprinkle mine in early May and watch bud clusters fatten within weeks!
Aim to work the amendment into the topsoil gently, then water in to activate uptake. Balanced nutrition now means bigger, longer-lasting flower flushes come July and August.