“Japanese maple” covers a huge range of plants. The Morton Arboretum notes there are hundreds of cultivars, and they vary a great deal in size, shape, leaf color and hardiness. Some stay as knee-high mounds for years. Others become small trees taller than a one-story house. The label on the nursery pot matters far more than the species name when you are deciding where to plant one.
The short answer: the species grows about 15 to 25 feet tall and 10 to 35 feet wide over many years. Upright cultivars such as ‘Bloodgood’ and ‘Emperor I’ reach about 15 to 18 feet. Weeping, cutleaf types such as ‘Crimson Queen’, ‘Tamukeyama’ and ‘Viridis’ usually stay 6 to 10 feet tall and a little wider. Growth is slow, so a young tree can take decades to reach full size.
Mature size of the species
| Source | Height | Width |
|---|---|---|
| The Morton Arboretum | 15 to 25 ft | 15 to 35 ft |
| NC State Extension | 15 to 25 ft | 10 to 25 ft |
Both describe the growth rate as slow. NC State describes the typical form as a short tree with a low, dense, rounded top and spreading, layered branches. Most garden plants are grafted cultivars, and they can be grown as single-trunk or multi-stemmed small trees.
Sizes of popular varieties
The Morton Arboretum lists these cultivars as successful in zone 5 when properly sited:
| Variety | Form | Size (height x width) | Leaves |
|---|---|---|---|
| ‘Bloodgood’ | Rounded tree | 18 x 18 ft | Purple-red, not dissected |
| ‘Emperor I’ | Upright, rounded | 18 x 16 ft | Purple-red, late to leaf out |
| ‘Shishigashira’ (Lion’s Head) | Vase-shaped | 15 x 10 ft | Crinkled, deep green |
| ‘Orangeola’ | Weeping | 8 x 8 ft | Dissected, orange in spring and fall |
| ‘Viridis’ | Weeping | 8 to 10 x 8 ft | Dissected, green |
| ‘Tamukeyama’ | Weeping or mounded | 10 x 12 ft | Dissected, crimson to purple-red |
| ‘Crimson Queen’ | Weeping or mounded | 6 x 8 ft | Dissected, purple-red |
The pattern is simple. Upright types with broad, non-dissected leaves are the big ones. Weeping types with lacy, cutleaf foliage stay low and spread sideways.
How fast do they grow?
Slowly. Both the Morton Arboretum and NC State rate Japanese maple as slow-growing. Any Japanese maple takes many years to fill out. Plant for the size the tag gives at maturity, not the size you see in the pot.
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What affects the final size
- Light. NC State recommends dappled shade, and the Morton Arboretum lists partial sun. Trees in harsh afternoon sun often scorch and grow less.
- Water. The Morton Arboretum notes Japanese maples do best with a consistent supply of water and that dry soils lead to leaf scorch. NC State adds that the species is not drought tolerant.
- Soil. Both sources call for moist, well-drained soil rich in organic matter.
- Wind. NC State recommends protecting the tree from drying winds.
- Climate. NC State lists hardiness zones 5a to 8b. The Morton Arboretum notes not all cultivars are fully hardy in zone 5 and some may need winter protection. A tree that dies back in hard winters will stay smaller.
- Pruning. Light, careful pruning can keep a Japanese maple compact, but it cannot turn a 20-foot cultivar into a 6-foot one without ruining its shape.
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THIS MUCH SOUGHT AFTER DWARF HAS PURPLE LEAVES IN DENSE CLUSTERS WITH SMALL INTERNODES
A new Japanese maple selection displaying a dwarf, compact form with small deep red leaves
Choosing the right size for your space
The ISA recommends choosing a tree whose mature size fits the site, above and below ground. With Japanese maples, that means:
- Measure the space, including the width. Weeping types are often wider than they are tall.
- Check what is overhead. The Morton Arboretum lists Japanese maple as suitable for planting under utility lines, but tall upright cultivars can still reach low wires over time.
- Allow room from the house. An upright type that will be 18 feet wide should be planted at least half that width, 9 to 10 feet, from walls so the branches have space. See how far from the house to plant a maple.
- Pick the form. For a small patio bed or a container, choose a weeping cutleaf type. For a small shade or specimen tree, choose an upright type like ‘Bloodgood’.
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Growing in containers
Weeping cutleaf forms are popular in large pots because they grow slowly. In a container they stay smaller than in the ground, but they dry out much faster. The Morton Arboretum advises checking container plants daily in warm weather and watering until water runs from the drainage hole. Roots in pots are also more exposed to winter cold.
Common problems that slow growth
The Morton Arboretum notes Japanese maples are susceptible to anthracnose, verticillium wilt and leaf scorch, which can be a problem in dry, sunny sites. NC State lists Japanese maple scale and aphids among common insect pests. A healthy, well-sited tree is the best defense.
If your Japanese maple is in the wrong spot, it can be moved while it is still small; see how to transplant a Japanese maple. For pruning timing, read what is the best month to trim a maple tree.
Sources
- Japanese Maple, The Morton Arboretum
- Acer palmatum (Japanese Maple), NC State Extension Gardener Plant Toolbox
- Watering Trees and Shrubs, The Morton Arboretum
- Tree Selection, International Society of Arboriculture, TreesAreGood.org
Top photo: Jeremy Reding, CC BY-SA 2.0, via Wikimedia Commons