How to Prune begonia 'Marmaduke'?
No pruning required

begonia 'Marmaduke' · Begonia 'Marmaduke'
Under glass grow in light, well-drained loam-based or loam-less potting compost in bright filtered light with shade from hot sun at an optimum of 19°C. Water moderately when in growth and apply a balanced liquid fertiliser at alternative waterings. Keep barely moist over winter. See Begonias: houseplants for further advice.
No pruning required