How to Propagate Iris 'Charming Billy'?
Propagate by division of the rhizome shortly from mid-summer to early autumn. See dividing irises

Iris 'Charming Billy' · Iris 'Charming Billy'
Grow in any moist but not waterlogged, neutral to slightly acidic soil in full sun or partial shade. In drier soils, dig in well-rotted manure before planting and apply as a mulch each spring
Propagate by division of the rhizome shortly from mid-summer to early autumn. See dividing irises