Butterfly bush, known botanically as Cassia bicapsularis, is a flowering woody shrub that blooms in yellow in the fall and winter. Butterfly bush has a spreading growth habit and reaches up to 10 feet in height and spread at maturity. The flower petal arrangement resembles a butterfly, thus the name. It is hardy in USDA zones 9 through 11 and thrives in full sun and moist soil. Butterfly bush benefits from light pinching and pruning in the fall and only occasional heavier pruning for shape, size or interior rejuvenation in the early spring.
Pinch back or prune the young tender branch tips in September to encourage additional branching and ensure fullness and abundant bloom. Take down just the end inch or two on each branch, placing the cut just above a leaf axil or bud.
Prune away diseased, damaged, dead or otherwise compromised branches and foliage in the fall to keep the plant tidy and disease free and make room for late-fall and winter blooms. Remove only as much plant tissue as necessary to preserve bloom capacity.
Cut back any crossing or abrading branches in the interior of the plant and tangled or congested branches that prevent sunlight penetration into and good airflow through the interior of the bush.