How to Prune plantain lily 'Spilt Milk'?
Remove spent foliage as required and clear up dead foliage when it dies back at the end of the growing season

plantain lily 'Spilt Milk' · Hosta 'Spilt Milk'
Grow in fertile, moist but well-drained soil in part shade with shelter from cold, dry winds. See hosta cultivation
Remove spent foliage as required and clear up dead foliage when it dies back at the end of the growing season