How to Propagate Iris 'Rocket'?
Propagate by division of rhizomes from midsummer to early autumn. See dividing irises

Iris 'Rocket' · Iris 'Rocket'
Grow in well-drained, fertile, neutral to slightly acidic 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
Propagate by division of rhizomes from midsummer to early autumn. See dividing irises