Pieris are a spectacularly colourful spring shrub for the garden or container
Pieris japonica are a species of fantastic evergreen spring shrubs which put on a spectacular display of white or pink bell-shaped flowers and colourful new growth which ranges from pale pink to dark burgundy. They are a member of the heather family and are originally from the forested mountain regions of China, Japan and Taiwan, and often called ‘Lily-of-the-Valley ‘ shrub. They are shrubs or small trees which in the wild can reach a height of 10m (33’), but the cultivated varieties available from garden centres are more likely to be small and compact or just reaching a height of 1 – 4m (40” – 13’). They are fairly 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. Strong 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 colour of the new growth won’t be as intense. They need well-drained but moisture retentive humus-rich acid soil. If you have an 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, particularly if there is a long dry spell.
It requires little or no pruning as it grows very slowly, just take 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 colourful 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 fertiliser, which also feeds rhododendrons, azaleas and camellias, in spring. Yellowing of the foliage is an indicator that it is lacking 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 plants requirements. Put a good layer of crocks in the bottom, about 5cm (2”), 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 pot 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 which 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 Provado Ultimate Bug Killer in early summer. Be careful about spraying other flowering plants as you will also kill bees, pollinators and any other beneficial insects. At the moment these seem to be confined to southern England.
'Flaming Silver’ – a lovely variegated variety with pink new growth and large sprays of white flowers. It is ideal for a small garden or container as it only reaches a height of 1m (40”) after 20 years.
‘Forest Flame’ – the most widely sold variety which can reach a height of 2.5m (8’). It has pale pink to bright red new growth and white flowers.
‘Katsura’ – has dark green glossy leaves and dark maroon new growth. It is ideal for a small garden or container as it only reaches a height of 1m (40”) after 20 years.
‘Little Heath’ - a compact variegated variety ideal for a small garden or container as it only grows to about 60 – 100cm (24 – 40”), unfortunately the flowers are a bit sparse. ‘Little Heath Green’ is not variegated.
‘Mountain Fire’ – produces a lot of white flowers and bright red new foliage. It reaches a height of 1.8m (6’).
‘Valley Valentine’ – grows to a height and spread of about 2.1m (7’) and produces dark pink/red flowers and lovely colourful new growth.
If you are looking for spring colour in the garden check out our other blog articles: 'Best tips for growing rhododendrons, azaleas and camellias', 'How to grow Japanese maples' and 'How do I improve the fertility of the soil without using chemicals?'