How to Propagate tall bearded iris 'Tall Chief'?
Propagate by division of rhizomes after flowering, from midsummer to late summer; for more advice, see dividing irises

tall bearded iris 'Tall Chief' · Iris 'Tall Chief'
Plant in full sun in well-drained soil, and with the top surfaces of the rhizomes exposed so that they get baked in summer sun, which encourages flowering. See bearded iris cultivation
Propagate by division of rhizomes after flowering, from midsummer to late summer; for more advice, see dividing irises