How to Prune tall bearded iris 'Benton Primrose'?
Cut down old flower stems after flowering, and remove any dying foliage in autumn

tall bearded iris 'Benton Primrose' · Iris 'Benton Primrose'
Plant in full sun in well-drained soil, and with the top surfaces of the rhizomes exposed so that they bake in summer sun, which encourages flowering. See also bearded iris cultivation
Cut down old flower stems after flowering, and remove any dying foliage in autumn