Prune a pieris japonica around April, after the blooms have faded, by deadheading the flowers and taking off all the dead and broken branches. By not deadheading and pruning off the faded flowers, it will fruit and then not flower as profusely the following year.
Pieris japonica is also known as the lily-of-the-valley shrub or Japanese pieris. It is a broadleaf evergreen, with lily-of-the-flower-like clusters of flowers and deep green leaves. It is hardy in the USDA Hardiness Zones of 5 through 8, preferring a well-drained rich soil that is mildly acidic with morning sun and afternoon shade, according to SFGate.
Pieris japonica pruning should be done by sanitizing the pruning implements to keep disease away. Take the faded flower cluster at the stem without damaging the neighboring growth buds. Dead stems can be pruned to the ground without worry or damage to the plant. Broken branches should be taken to the strongest lateral branch for best results. Pieris japonica plants can be damaged by frost but are likely to recover with good maintenance.
The leaves of a pieris japonica are poisonous and should not be ingested. Care should be taken to plant them away from livestock and small children.