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Acer japonicum

Fullmoon maple

Sapindaceae

Japan: Hokkaido, Honshu, Shikoku, and Kyushu

Attracts Pollinators Container Friendly

SunPart Shade – Full Sun

WaterMedium

HardinessZones 5–7

Overview

Acer japonicum is a deciduous tree or large multi-stemmed shrub reaching 20-30 feet (6-9 m) tall and about as wide, with a rounded, layered crown and smooth grey bark. Leaves are nearly circular, 3-6 inches (7.5-15 cm) across, with 9-11 shallow lobes cut about one third of the way to the centre, and carry soft hairs on both surfaces when young. Autumn colour runs through yellow, orange, scarlet, and crimson, often with several shades on one branch, and holds two to three weeks in October. Purple-red flowers 0.4 inch (10 mm) across hang in corymbs of 10-15 on 1-2 inch (2.5-5 cm) stalks in April and May, opening with or just before the leaves. Paired samaras 0.8-1.2 inches (2-3 cm) long spread their wings almost horizontally and ripen from green to brown by October. Annual extension is 6-12 inches (15-30 cm), so a specimen takes 20-30 years to fill its mature dimensions. Leaf margins scorch where summer afternoons pass 85 F (29 C) in dry air, and the species declines in the humid heat of USDA zones 8 and warmer. Verticillium wilt causes branch dieback in infected soils. Hardy in USDA zones 5-7.

Native Range

Acer japonicum is native to Japan, occurring on Hokkaido, Honshu, Shikoku, and Kyushu. It grows in cool mountain woodland between 1,600 and 5,600 feet (500-1,700 m), usually on north-facing slopes and along stream margins under a canopy of Fagus crenata and conifers. Rainfall across that range passes 60 inches (1,500 mm) a year, with cool summer nights.

Suggested Uses

Planted as a specimen in courtyards, woodland gardens, and shaded lawns where the October colour sits in view. Used at pond edges and along paths, and grown in 25 gallon (95 L) containers with root pruning every three years. The spreading crown reaches 20-30 feet (6-9 m) wide, so plantings sit 15 feet (4.5 m) or more from structures.

How to Identify

Leaf blades are almost round in outline with 9-11 lobes cut no more than halfway to the base, against the 5-7 lobes of A. palmatum, where the cuts reach two thirds or more toward the leaf base. New leaves and leaf stalks carry soft white hairs that thin as the season goes on. Flower corymbs hang below the emerging leaves on stalks 1-2 inches (2.5-5 cm) long. Samara wings spread to nearly 180 degrees, flatter than the 90-120 degree angle in A. palmatum.

Appearance

Size & Dimensions

Height20' - 30'

Width/Spread20' - 30'

Reaches mature size in approximately 30 years

Colors

Flower Colors

red

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~2 weeks

Spring

Corymbs open in April in USDA zone 7 and in early May in zone 5, at or just before leaf expansion. Flowering lasts 10-14 days, with purple-red sepals and petals held on pendulous stalks below the new shoots. Fruit set follows within three weeks, and samaras ripen from green through a pink flush to brown by October. Trees begin flowering at about eight to ten years from seed.

Detailed Descriptions

Foliage Description

medium green in summer, turning yellow, orange, scarlet, and crimson in autumn

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Sun

Requires 3-6 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 - 6.5(Acidic)

357912

Soil Types

loam silt sand

Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

20-30 years

Care & Maintenance

Care Guide

Three to six hours of morning sun with shade through the afternoon suits the species in USDA zones 6-7; full sun works only where summer maxima stay under 80 F (27 C). Soil is moisture-retentive loam at pH 5.0-6.5, and 2-3 inches (5-8 cm) of leaf-mould mulch over the root zone holds moisture while staying clear of the trunk. Water use is about 1 inch (2.5 cm) per week, and the shallow root system dries out within three or four days in sandy ground. Fertiliser is limited to a spring application of a low-nitrogen formulation at 0.5 pound per 100 square feet (250 g per 9 sq m), since soft growth scorches faster. Verticillium wilt, anthracnose, and aphids with the sooty mould that follows them occur across cultivated plantings. Wind above 25 mph (40 km/h) tears the thin leaf blades.

Pruning

Cutting is done in December and January while the tree is dormant, since sap runs heavily from cuts made in late winter and early spring. Work is limited to dead, crossing, and rubbing branches, plus thinning that opens the layered branch structure. The natural crown form is lost where leaders are shortened, and regrowth from such cuts is congested and upright. Cuts larger than 2 inches (5 cm) in diameter close slowly and open a path for decay.

Pruning Schedule

winter