How to Prune sweet galingale?
Trim off old foliage to just above the level of the water in autumn

sweet galingale · Cyperus longus
Also known as: cypress root; galingale; long cyperus; sweet cyperus; sweet cypress
Grow in moisture-retentive soil, can be grown as marginal or bog plant in sun or light shade. Can be grown in large containers to prevent spread of invasive roots
Trim off old foliage to just above the level of the water in autumn