How to Prune iris 'Purple Magic'?
Old flower stems can be cut down after flowering

iris 'Purple Magic' · Iris 'Purple Magic'
Grow in well-drained, fertile, neutral to slightly acid soil in full sun. Do not cover the rhizomes with mulch, or allow other plants to shade them; sun on the rhizomes encourages flowering. Give a high-potash feed in spring and divide every three to four years. See also Bearded iris cultivation
Old flower stems can be cut down after flowering