Kerria japonica 'Pleniflora', double kerria
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Deciduous Shrubs

Kerria japonica 'Pleniflora'

double kerria

RosaceaeAsia

At a Glance

TypeShrub
HabitSpreading
FoliageDeciduous
Height5–8 feet (1.5–2.4 m)
Width6–9 feet (1.8–2.7 m)
Maturity4 years

Growing Zones

USDA Hardiness Zones

4 - 9
Zone 4
Zone 5
Zone 6
Zone 7
Zone 8
Zone 9
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Overview

Kerria japonica 'Pleniflora', commonly called double kerria, is a vigorous deciduous shrub in the family Rosaceae — the double-flowered cultivar of the Japanese kerria, known in cultivation since before 1834. It produces abundant, rounded, pompom-like double flowers 1–1.5 inches (2.5–4 cm) across composed of numerous narrow petals, bright golden-yellow and globular in form, covering the arching branches in April and May. The double-flowered form makes a bolder, denser display than the single-species K. japonica and tends to be somewhat more vigorous and upright, typically reaching 5–8 feet (1.5–2.4 m) tall and spreading 6–9 feet (1.8–2.7 m) wide by root suckers. Like the species, it has distinctive bright green, zigzag-angled stems that remain photosynthetically active through winter — a feature of genuine year-round ornamental value. K. japonica 'Pleniflora' blooms on the previous season's old wood and is equally shade-tolerant, thriving in the dappled light of a woodland garden or on north-facing exposures where few yellow-flowering shrubs perform. Because the flowers are fully double and produce no accessible pollen, they have lower pollinator value than the single-flowered species. Alternate, ovate to lanceolate leaves 1.5–4 inches (4–10 cm) with doubly serrated margins; yellow autumn color.

Native Range

Kerria japonica is native to mountain slopes and forest margins of China and Japan. 'Pleniflora' is a cultivar of horticultural origin, known in cultivation in Europe since before 1834; it has no independent native range. Not native to North America.

Suggested Uses

Kerria japonica 'Pleniflora' is one of the boldest and most reliable yellow-flowering shrubs for Pacific Northwest shade and woodland gardens, offering a dense spring display of pompom flowers on a large, spreading, easy-care shrub that thrives in difficult low-light positions. Excellent massed on shaded slopes, woodland garden edges, north-facing borders, and under large deciduous trees. The green winter stems provide subtle year-round structure. Outstanding combined with spring bulbs, Helleborus, Pulmonaria, and Hosta in a shade border. A Great Plant Pick for Pacific Northwest gardens.

How to Identify

Double kerria is identified by its rounded, pompom-like, fully double golden-yellow flowers 1–1.5 inches (2.5–4 cm) across composed of numerous narrow petals, appearing on arching branches in April–May. The distinctive bright green, prominently zigzag-angled stems remain green and ornamentally attractive through winter. Leaves are alternate, ovate to lanceolate, doubly serrated, medium green. Distinguished from single-flowered K. japonica by its fully double, rounded pompom-like flowers (vs. flat, five-petaled single flowers); from Forsythia by its green zigzag stems and non-tubular flowers.

Appearance

Size & Dimensions

Height5' - 8'
Width/Spread6' - 9'

Reaches mature size in approximately 4 years

Colors

Flower Colors

yellow

Foliage Colors

green

Fall Foliage Colors

yellow

Bloom Information

Bloom Period

~3 weeks
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Spring
Kerria japonica 'Pleniflora' blooms in spring, typically April through early May in Pacific Northwest gardens, on the previous season's old wood over two to four weeks. The rounded, fully double, golden-yellow pompom flowers are produced in profusion along the length of the arching branches. The double-flowered cultivar may flower slightly later than the single-flowered species and tends to hold its flowers longer. Scattered late-season rebloom is possible but uncommon.

Detailed Descriptions

Flower Description

Golden-yellow; double pompom-like, 1–1.5 inches (2.5–4 cm), numerous narrow petals

Foliage Description

Alternate, ovate to lanceolate, 1.5–4 inches (4–10 cm), medium green, doubly serrated; yellow in autumn

Growing Conditions

Sun Requirements

Partial Shade
Full Shade
Tolerates up to 6 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.0 - 7.0(Neutral)
357912
Soil Types
loampeatclay
Drainage
well drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

3–5 years

Care & Maintenance

Care Guide

Plant in partial shade to full shade in moist, well-drained, humus-rich, acidic to neutral soil. Care requirements are identical to the single-flowered species: K. japonica 'Pleniflora' is shade-tolerant, performing and flowering well in conditions where most ornamental shrubs fail. Tolerates full sun in cool coastal Pacific Northwest conditions; may scorch in hot dry east-of-Cascades summers. Spreads freely by root suckers — remove at ground level to control spread. Largely pest- and disease-free; twig canker can blacken stems — cut affected stems to the base. Water moderately; established plants tolerate brief dry spells.

Pruning

Prune immediately after flowering (May–June). Each year, remove one-third to one-half of the oldest stems back to ground level to maintain vigor and an open, arching form. 'Pleniflora' can become a dense, congested thicket without regular thinning; annual renovation pruning keeps the plant flowering strongly and prevents a buildup of old woody stems. Avoid autumn and winter pruning — this removes next spring's flower buds. Remove suckers at any time to control spread.

Pruning Schedule

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late spring

Maintenance Level

low

Container Growing

Minimum container size: 10 gallons

⚠️ Toxicity Warning

Non-toxic