How to Prune commonName:"begonia 'Waterfall'"?
No pruning required

commonName:"begonia 'Waterfall'" · Begonia 'Waterfall'
In spring plant tubers, hollow side uppermost, in free-draining compost at 16-18°C. Plant out after the last frosts in fertile, humus-rich, moist but well-drained soil in sun or partial shade. Lift the tubers in autumn before the first frosts and dry off. See begonias: outdoors for further information
No pruning required