How to Prune Siberian iris 'Prussian Blue'?
Remove any dying foliage in autumn, old flower stems can be cut down after flowering

Siberian iris 'Prussian Blue' · Iris 'Prussian Blue'
Grow in any good garden soil that is preferably moist but not waterlogged. In drier soils, dig in well-rotted organic matter before planting then apply as a mulch each spring
Remove any dying foliage in autumn, old flower stems can be cut down after flowering