Begonias, like roses, should be deadheaded. "All varieties of begonias require grooming and pruning for a full compact plant," says VanWyk. According to Hilliard-Knapp, deadheading begonias is ...

Look for a variety that is slow release fertilizer with phosphorous. Begonia grandis does not require pruning since it doesn't grow particularly fast or large and it dies back every winter.