Japanese Andromeda (Pieris japonica)

Pieris japonica is a plant of many names. Also known as Japanese andromeda, flame of the forest or lily-of-the-valley bush, this striking evergreen shrub looks good all year round. With its attractive foliage and sprays of spring flowers, it’s a great low-maintenance shrub for shady gardens.

Common nameFetterbush. Japanese Andromeda, Japanese Pieris, Lily-of-the-Valley Shrub, Pieris
Botanical namePieris japonica
FamilyEricaceae
Speciesjaponica
OriginSE China, Central to Southern Japan, and Taiwan
Life cycleWoody
Plant typePerennial
Hardiness zone4, 5, 6, 7, 8
SunlightFull Sun
MaintenanceMedium
Soil conditionHigh Organic Matter
Soil phAcid
DrainageWell-Drained
Growth rateSlow
Spacing6 – ft. – 12 ft.
Harvest timeFall
Flowering periodSpring
Height8 ft. – 10 ft.
Width8 ft. – 10 ft.
Flower colorWhite
Leaf colorBrown, Copper
Fruit colorBrown, Copper
Stem colorGold, Yellow
Fruit typeCapsule
Leaf benefitShowy
Flower benefitFragrant
Garden styleAsian Garden

I. Appearance and Characteristics

Pieris japonica, the Japanese andromeda or Japanese pieris, is a species of flowering plant in the heath family Ericaceae. It is native to eastern China, Taiwan, and Japan, where it grows in mountain thickets. This medium-sized evergreen shrub or tree is widely cultivated in gardens.

Pieris japonica grows to 1–4 meters or 3.3 –13.1 feet tall, occasionally up to 10 meters, with alternate, simple leaves on brittle stems. The leaves open bronze or red in some cultivars, turning green. The trusses of small urn-shaped flowers are white or pink, appearing early in spring, and providing a decorative effect against the young red leaves. The flowers usually last two or three weeks.

Japanese Andromeda (Pieris japonica)

The plant is poisonous if consumed. The toxicity is a result of the grayanotoxins contained by the flowers and leaves. If flowers and leaves are ingested by humans, symptoms may include salivation, headaches, vomiting, cardiac failure, and death. Cattle, goats, horses, dogs, and cats may suffer similar symptoms after ingesting the leaves or flowers of this plant.

The name “andromeda” originated from an earlier genus name for the plant.

II. How to Grow and Care

Sunlight

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.

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.

Watering

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

Japanese Andromeda (Pieris japonica)
Common Bluebottle with Pieris japonica subsp. japonica (Matsudo, Chiba, Japan)
t-mizo
CC BY 2.0

Soil

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.

Fertilizing

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.

Pruning

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.

Japanese Andromeda (Pieris japonica)
Pieris japonica ‘Sarabande’ – Pieris japoński ‘Sarabande’
Babij
CC BY-SA 2.0

Propagation

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.

Potting and Repotting

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.

Mulch

To help suppress weeds and retain moisture, apply several inches of organic mulch to the shrub’s root zone, keeping mulch 4 inches from the woody stem. Pine needles are an excellent mulch for lily-of-the-valley shrubs because they add acidity to the soil as they break down.

Japanese Andromeda (Pieris japonica)
Pieris japonica – pink autumn foliage
Mary Hutchison
Public Domain Mark 1.0

Overwintering

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.

Pests and Diseases

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.

Common Problems

In addition to the common pest and disease issues, your Japanese pieris may exhibit other cultural symptoms.

Japanese Andromeda (Pieris japonica)
Japanese andromeda / Pieris japonica / 馬酔木(アセビ)
TANAKA Juuyoh (田中十洋)
CC BY 2.0
  • Yellowed Leaves

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.

III. How to Get 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.

Japanese Andromeda (Pieris japonica)
Pieris japonica ‘Little Heath’ – Pieris japoński
Babij
CC BY-SA 2.0

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.

IV. Uses and Benefits

Japanese pieris is a popular plant in yards and as a focal point in large gardens, prized for its bronzed foliage and showy pink and white winter flowers. The dense shrub is often used to create natural privacy barriers and it is an essential plant in any winter garden. Plant amaryllis with the flowering shrub for contrasting color in the early spring.

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