How to Prune broad-leaved bamboo?
Remove weak, dead, damaged or spindly stems in spring and thin to show off stems to best effect. Cut out any flowering shoots promptly to discourage more from forming - see bamboo cultivation

broad-leaved bamboo · Sasa palmata
Grow in fertile, humus-rich, moist but well-drained soil, best in partial shade. Protect from cold drying winds. Rampant, creeping rootstock can become very invasive in warm, moist or favourable conditions and need restraining as they have the potential to become a nuisance ; see bamboo control and bamboo cultivation
Remove weak, dead, damaged or spindly stems in spring and thin to show off stems to best effect. Cut out any flowering shoots promptly to discourage more from forming - see bamboo cultivation