Pieris japonica is a species of fantastic evergreen spring shrub that puts on a spectacular display of white or pink, bell-shaped flowers and colorful new growth, which ranges from pale pink to dark burgundy. It is a member of the Heath family and is originally from the forested mountain regions of China, Japan, and Taiwan, and often called Lily of the Valley Bush, Japanese Pieris, or Japanese Andromeda. It is a shrub or small tree which in the wild can reach up to 33 feet (10 m), but the cultivated varieties available from garden centers are more likely to be small and compact or just reaching a height of up to 13 feet (4 m). They are relatively slow-growing, so even if you buy one of the larger varieties, they will probably take up to 20 years to reach their maximum height. They are toxic to people and animals, so make sure they are planted in a position where farm stock cannot reach them. They go well with other ericaceous woodland plants such as Rhododendrons, azaleas, and Camellias, as they all enjoy the same conditions.
As they are originally from a forested habitat, they do best in dappled shade. Intense sun in early spring can burn the tender new growth. They will not do too well in full shade as they won't produce as many flowers, and the color of the new growth won't be as intense. They need well-drained but moisture-retentive humus-rich acid soil. If you have alkaline soil, you will have to grow it in a pot. You can add ericaceous compost and feed and mulch with pine needles, but it will only be temporary, and an alkaline soil will always be an alkaline soil. They are a hardy shrub, but it may need some protection from late frosts, which will burn the new growth and flowers. The frost probably won't kill the plant, but it will mar the spring display, which is usually the main reason it is grown.
Plant them to the same depth as they are in the pot and water well. Keep an eye on the watering in the first season, mainly if there is a long dry spell.
It requires little or no pruning as it grows very slowly, just takes out any dead branches. If you have to prune, do it immediately after flowering. Take off the spent flowers to encourage the plant to put its energy into producing colorful new growth. Mulching with pine needles or ericaceous compost in spring will conserve moisture and retain the acidity of the soil. Feed with an ericaceous fertilizer, which also feeds Rhododendrons, azaleas, and Camellias, in spring. Yellowing of the foliage is an indicator that it lacks nutrients.
Choose a container in proportion to the plant, and by re-potting, every couple of years eventually move up to a pot suitable for the plant's requirements. Put a good layer of crocks in the bottom, about 2 inches (5 cm), to aid with drainage. Pot up in ericaceous compost and raise the pot off the ground on pot feet, a couple of bricks or stones. This ensures that the water runs clear away from the container and doesn't block the drainage hole with silt. It will be more susceptible to drying out so keep an eye on the watering. A lack of nutrients can also be a problem so make sure you feed in spring.
Pests and Diseases
Leaf spot is a fungus which can be a problem in a wet spring. Spray with a fungicide to control the spread. There is no non-chemical solution.
Phytophthara ramorum is a particularly vicious fungus which attacks the roots and is responsible for Sudden Oak Death. The first sign is a wilting plant which is not dry or sat in saturated soil. There is no control. Dig the plant up and either burn it or put it in the grey refuse bin. Don't compost it or put it in the green waste bin as this will only spread the disease.
Pieris Lacebug is a winged insect that causes the leaves to be pale and mottled on the upper surface, eventually leading to a bleached appearance later on in summer. The insects can be seen on the underside of the leaf. There is no non-chemical control. Spray with insecticide in early summer. Be careful about spraying other flowering plants as you will also kill bees, pollinators, and any other beneficial insects.