How to Prune Kahili ginger?
No pruning required other than cutting back the foliage and old flower spikes at the end of the season

Kahili ginger · Hedychium gardnerianum
Also known as: Kahli ginger lily
Outdoors, grow in humus-rich, moist but well-drained soil in sun or partial shade. Shelter from cold winds and consider applying a deep mulch of garden compost or leafmould to protect the rhizomes in frost prone areas. In containers or under glass, use a loam-based compost such as John Innes No 3 and grow on in bright indirect light
No pruning required other than cutting back the foliage and old flower spikes at the end of the season