How to Prune yellow flag 'Roy Davidson'?
Remove any dying foliage in autumn, old flower stems can be cut down after flowering

yellow flag 'Roy Davidson' · Iris pseudacorus 'Roy Davidson'
Grow in moist to wet, deep, humus-rich, acid soil; it thrives at the margins of large ponds or streams; has the potential to become a nuisance if not managed well so plant with care
Remove any dying foliage in autumn, old flower stems can be cut down after flowering