Japanese pieris (pee-eh-ruhs) is a broadleaf evergreen shrub in the heath family, boasting year-round beauty and interest when used as a landscape plant. Native to Japan, Taiwan, and east China, Japanese pieris has oblong leaves that open with a reddish-bronze color before transforming into a glossy, leathery green. It is an early bloomer, erupting in drooping clusters of delicate flowers for about two weeks during the late winter and early spring.
The white or pale pink blooms resemble those of lily-of-the-valley, without the strong, notable fragrance. Best planted from potted nursery plants in the spring or fall, Japanese pieris is not fast-growing and it will take its time establishing itself in your landscape. Because of its slow growth habit, the plant makes a good choice for foundations and shrub borders—you don't run the risk of damaging nearby structures or losing control of the plant's growth or spread.
Japanese pieris is toxic to dogs and cats, and it is considered to be seriously toxic to humans. It contains grayanotoxins that can pose hazards even with minor ingestion.
|Common Name||Japanese pieris, Japanese andromeda, lily-of-the-valley shrub|
|Botanical Name||Pieris japonica|
|Mature Size||9–12 ft. tall, 6–8 ft. wide|
|Sun Exposure||Full, partial|
|Soil Type||Moist but well-drained|
|Bloom Time||Winter, spring|
|Flower Color||White, pink|
|Hardiness Zones||4–8 (USDA)|
|Toxicity||Toxic to humans, pets|
Japanese Pieris Care
Japanese pieris is well-loved for its ease of care and year-round interest. It is important to plant the specimen at the same depth as it was growing in its nursery container, as planting too deep may prevent the plant from flowering. Getting the sun exposure right is also critical—in warmer climates, it should be regarded as a plant for partial shade, while gardeners in cooler climates can treat it as a full-sun plant. Japanese pieris plants like to be partially shielded from especially rough weather conditions, such as intense wind or rain. Once the shrub is established, you shouldn't have to do much pruning—the natural growth habit of a healthy shrub is quite attractive. Removing spent flowers after blooming will keep your shrub looking neat.
In cooler regions, Japanese pieris plants prefer to grow under full sunlight, getting at least six to eight hours a day. But in warmer climates, it's better to plant your Japanese pieris in a partial shade location that shields it from the harsher afternoon light. Southern gardeners often view this plant as a shade lover, but it does need morning sun to bloom its best, while afternoon shade prevents scorching.
Plant your Japanese pieris in soil that is rich in organic matter, moist, and well-draining. The plant does not do well in soggy blends and can be susceptible to root rot if its soil retains too much moisture. Japanese pieris plants love soil with an acidic pH level (5.1 to 6.0); before planting, check the soil pH—if you find you need to increase its acidity, you can add a specialized fertilizer for azaleas, camellias, and rhododendron, which are also acid lovers.
Japanese pieris plants need regular, deep watering about once a week, either from natural rainfall or manual methods. Generally, you should aim to keep the soil consistently moist down to about 3 inches deep. A top layer of pine needle mulch, about 2 to 3 inches thick, can also help to retain moisture. But at the same time, these plants cannot tolerate having their roots soaking in standing water; they will often fail quickly in dense soils that fail to drain. Maintaining a proper moisture level (moist but not wet) can be a challenge with these shrubs.
Temperature and Humidity
As long as it's planted in the proper hardiness range (USDA zones 4 to 8), Japanese pieris does not have any special temperature requirements. Do your best to protect the plant from cold or especially harsh winds, which can result in leaf browning or die-back.
A native plant of the mountain thickets of Japan and East China, Japanese pieris does equally well in dry and moderately humid conditions, though intensely hot, humid weather can encourage fungal diseases, such as leaf spot. Space the plants well apart to keep good air circulation. Plants that seem susceptible to fungal disease should be pruned to improve air circulation.
Add a fertilizer formulated for azaleas, camellias, and rhododendron in mid-February and mid-May, following the package instructions for the amount. Mulching with an acidifying organic material such as pine needles can also help provide nutrients.
Types of Japanese Pieris
There are numerous cultivars of Japanese pieris that vary in hardiness, size, flower color, and bloom time, including compact cultivars that are suitable for containers. Some of the most popular cultivars include:
- 'Mountain Fire': This variety is one of the most popular cultivars, thanks to its vibrant red-orange foliage. It has a compact growth habit and will grow to be about 4 feet tall and 3 feet wide over 10 years.
- Pieris japonica var. yakushimensis 'Cavatine': This dwarf cultivar grows to only about 2 feet tall and wide. It has an abundance of creamy-white, bell-shaped blossoms and blooms later than most, around late April or early May.
- 'Valley Rose': This plant is a compact, rounded cultivar with light pink flowers that bloom in late winter or early spring. It grows to between 3 and 5 feet tall and wide and is hardy in USDA zones 6 to 8.
- ‘Dorothy Wyckoff’: This compact variety grows vigorously, reaching about 5 feet tall and wide at maturity. It boasts deep red buds, pale pink flowers, and is especially well-suited to container growing.
- 'Red Head': This cultivar produces a splash of red color in the landscape, as the new growth emerges as brilliant red before transforming to green.
- 'Flaming Silver': This is a variegated cultivar with silver and green foliage that replaces red to pink new growth. It has white flowers.
- 'Pink Delight': This type has pale pink blossoms. The foliage is bronze when it emerges, transforming to green.
- 'Little Heath Green': This cultivar is a great compact plant, growing to just 30 inches tall.
Regular deadheading of spent flowers will keep this plant from setting seed, which encourages continued blooming. Generally speaking, additional pruning is usually unnecessary, as the plant is quite attractive in its natural state. However, if a shrub is underperforming or prone to fungal disease, you may want to do a more disciplined pruning every few years. Begin by removing any damaged or diseased branches, using sharp loppers. Cuts should be made about 1/2 inch above a leaf bud. Then, trim off the top of the shrub to the desired height. Next, cut away up to one-fourth of the inner branches to open up the center to light and air. Finish up by shaping the outside of the plant to the desired shape.
Propagating Japanese Pieris
This shrub is best propagated by taking softwood cuttings from the stem tips during the active summer growing season. Here's how to do it:
- Use sharp pruners to clip 6- to 8-inch cuttings off the green tips of actively growing stems.
- Remove the bottom leaves of the cutting, then use a sharp knife to scrape off the bark from the bottom 2 inches. Dip the scraped end in rooting hormone.
- Plant the cutting in a small, well-draining container filled with dampened commercial potting mix.
- Place the pot in a protected location where it can be sheltered from the direct midday sun. The best temperature will be 65 to 75 degrees Fahrenheit.
- Monitor the pot, moistening the potting mix when it becomes dry. In six to eight weeks, the cutting should develop a good network of roots. Continue growing the sapling in its pot until late fall, when you can plant it in the landscape.
How to Grow Japanese Pieris From Seed
Although it's not a common method of propagation, Japanese pieris can be grown from seeds collected from mature seed pods. Collect the seeds in late fall and save them until the following summer, when you can plant them in the garden or small pots. Plant the seeds so they are just barely covered, and keep moist until they germinate and sprout, which usually takes two to four weeks. Ideal temperatures for germination are 70 degrees Fahrenheit during the day and 60 degrees at night. Give the new seedlings shelter from the direct sun. If starting the seeds in pots, they can be transplanted into the garden in the late fall. Make sure to harden off seedlings before planting in the garden.
Potting and Repotting Japanese Pieris
Smaller cultivars of Japanese pieris are sometimes grown in containers. Use a large, well-draining container filled with a lightweight potting mix, adding acidic fertilizer, which will provide the acidity these plants prefer. Monitor pots frequently and water deeply whenever the top inch of potting mix becomes dry. Potted pieris plants will require more regular feeding than garden plants; use a water-soluble acidifying fertilizer every month.
Common Pests and Plant Diseases
Japanese pieris can be affected by several fungal diseases—including leaf spot and phytophthora root rot—which can spread especially easily in humid weather. Because of this, proper spacing—whether you plant more than one pieris or other shrubs nearby—is crucial for good air circulation and plant health. Allow about 6 to 7 feet between shrubs, and keep in mind their mature size. Seriously advanced root rot will probably be fatal, requiring that you remove the plant.
Common pest issues for Japanese pieris plants include nematodes, mites, and lace bugs, which suck on the leaves, making them yellow and unsightly. Treat any signs of pest issues using a horticultural oil, such as neem oil.
No special winter protection is needed for garden shrubs, provided you are growing them within the recommended hardiness range. Container-grown shrubs will benefit from moving them into a sheltered location, especially in zones 4, 5, and 6.
How to Get Japanese Pieris to Bloom
Failure to bloom is not a common occurrence but is sometimes the result of a plant having been planted too deep. Japanese pieris should be planted at the same depth as it was growing in the nursery container. If your new shrub fails to bloom, try digging it up and replanting so the root ball is slightly higher.
Unusually cold winter or spring temperatures can sometimes kill the flower buds, resulting in a spring season with few or no blooms. The shrub generally returns to a normal bloom pattern in the next season. Excessive fertilization often results in vigorous foliage growth at the expense of flowers. It can sometimes take a year or two for the shrub to return to normal blooming behavior after severe overfeeding. If your shrub stops blooming after you begin to feed it, withhold all feeding to see what impact this makes.
Too little sunlight can also result in poor blooms. While the plant needs protection from intense southern sunlight, it does still require adequate light to bloom, Plant where it will receive morning sunlight and afternoon shade in southern climates. In cooler climates, plant it where it will receive full sun.
Common Problems With Japanese Pieris
In addition to the common pest and disease issues, your Japanese pieris may exhibit other cultural symptoms:
Yellowed leaves are often a symptom of chlorosis caused by a soil pH that is too alkaline. Japanese pieris is an acid-loving plant. If you notice yellowed leaves, try feeding the plant with an acidifying fertilizer, or establish a routine of amending the soil with an acidifying amendment, such as pine needles.
Leaves Wilt, Stems Sag
These symptoms are sometimes misdiagnosed as a lack of water. In reality, wilting leaves and stems usually indicate that your shrub is getting too much water—phytophthora fungal infection may already be underway. If you notice this wilting problem, reduce watering to allow the top 1 to 2 inches of soil to dry out completely before irrigating again.
Leaf Edges Burned
When the edges of the leaves turn brown and burned and the tips of branches begin to die back, it is generally because your Japanese pieris is getting too much direct midday sun. This is most common in warmer climates, where the plants prefer some shelter during the hottest hours of the day. In zones 7 and 8, gardeners should usually seek a partial shade location for this plant.
How can I use this plant in the landscape?
Best planted alongside or among other shrubby plants with similar acidic soil preferences, such as rhododendrons. It works well in shrubby borders, as foundation plantings, or as a specimen plant. With leaves similar to those of rhododendron, Japanese pieris is a good addition to Asian-themed gardens.
Can I move a Japanese pieris shrub?
The most common reason to move these shrubs is to correct sun exposure or soil pH issues. Moving Japanese pieris is more successful with younger plants, but even well-established shrubs can often be moved—fall is the best time. Make sure to water the plant well for a day or two before you move it. Dig a circular trench at least 12 inches deep around the perimeter of the shrub's drip line, then lever the plant up out of the ground onto a tarp or piece of plastic. Slide the entire plant to its new location, then plant it into a well-prepared hole at the same depth.
How long does a Japanese pieris shrub live?
Like many slow-growing shrubs, Japanese pieris has good longevity. Lifespans of up to 40 years are common.
Safe and Poisonous Garden Plants. University of California.