How to Prune powdery alligator-flag?
Remove old flowers and leaves regularly

powdery alligator-flag · Thalia dealbata
Under glass, grow in baskets of loam based compost in full light. Grow as a marginal aquatic in a planting basket of fertile, loamy, humus-rich soil in up to 15cm of water at the edge of a sunny pool. In colder areas it will become deciduous
Remove old flowers and leaves regularly