Yellow bells are hardy plants that can withstand vigorous pruning. Cutting back old growth and removing dead or diseased branches creates a stronger plant that produces more blooms. Gloves and pruning shears are the only tools required.
Prune after the blooms fade
Blooms fade in late spring or early summer. Pruning after the blooms fade will increase the number of blooms that appear on the plant the next season. Prune in a random, informal pattern. More formal shapes may reduce the number of buds on the plant, resulting in fewer blooms.
Remove dead and diseased branches
Dead and diseased branches can be lopped off at any time of the year. Removal reduces stress on the plant and is suggested for regular maintenance. Cut branches to the necessary length required to maintain the desired shape.
Remove old growth
Remove one-fourth of the old growth of a mature plant to within a few inches of the base. On younger plants, remove old growth from the center of the plant to facilitate air circulation. Aggressive pruning of neglected plants requires cutting all branches back to within a few inches of the ground. The plant grows and regains its original shape within two years.