Pieris japonica, also commonly known as lily-of-the-valley bush and Japanese Andromeda, is a large shrub with highly decorative buds, long flower panicles and fruits. Native to Japan, Taiwan and Eastern China, Pieris Japonica grows up to 3.5 metres (12 feet) tall and 3 metres (10 feet) in width. Its growing habit makes for short branches with very dense green razor-tooth edged leaf foliage. Depending on the varietal, Pieris can flower with white to hues of pink and deep red blooms. Pieris japonica responds well to deadhead pruning as individual blooms die off, which keeps the plant from fruiting and will bloom more profusely next cycle. An overall annual or biennial pruning for size and shape should be done in the spring or summer after a bloom.
Cut away individual spent blooms with your secateurs at the base of the bloom stem where it meets the branch. Make your cut in the flower stem at least 1.5 mm (1/16 inch) above the main branch so as not to damage the branch itself. Weekly maintenance of this kind will encourage more profuse blooming next season.
Begin annual or biennial pruning by cutting away any damaged or diseased branches with your secateurs or loppers, removing as much as necessary to clear away the damage and leaving approximately 13 mm (1/2 inch) above a flower bud or leaf axil.
Use loppers to prune the height of the shrub once a year or every other year. Also use the loppers or secateurs to establish your desired top shape, either flat, rounded or jaggedly naturalistic.
Cut away up to one quarter of the internal branches to thin and shape the interior of the plant and open it up for light and air penetration if needed.
Shape the perimeter of the Pieris with loppers on the thick branches and the secateurs on smaller branches as needed. Make cuts 6-7 mm (1/4 inch) above bud and leaf axils where possible to preserve bloom capacity.
Pieris japonica produces flowers on its previous season's growth. Because of this, you should never prune it back in winter as you will destroy the flower buds for the following bloom cycle.