Crimson King is a purple-leaved cultivar of Norway maple (Acer platanoides) that holds deep maroon foliage from spring to fall. It is tough, hardy to about zone 3, and tolerates urban conditions, which is why it was planted so widely in mid-century yards. It also has real drawbacks: very dense shade that kills lawns beneath it, shallow roots that lift sidewalks, susceptibility to verticillium wilt and girdling roots, and the invasiveness of its parent species, which has led some states to restrict its sale. If you already have one, it can be kept healthy for decades with good care. If you are deciding whether to plant one, there are better purple-leaf choices for most gardens. Here are the pros, cons, care steps and alternatives.
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In this guide
Key Takeaways
- Hardy in about zones 3 to 7; grows roughly 35 to 50 feet tall and 30 to 40 feet wide.
- Pros: reliable purple color, cold hardiness, tolerance of compacted and urban soils.
- Cons: dense shade and surface roots, verticillium wilt, girdling roots, and invasive seedlings from the parent species.
- Norway maple sale is restricted in some states, including Massachusetts and New Hampshire; check your state list.
- Alternatives include ‘Forest Pansy’ redbud, purple smoke tree, purple-leaf Japanese maples and copper beech.
Crimson King at a Glance
| Trait | Details |
|---|---|
| Botanical name | Acer platanoides ‘Crimson King’ |
| Hardiness | About USDA zones 3 to 7 |
| Mature size | About 35 to 50 ft tall, 30 to 40 ft wide |
| Growth rate | Moderate, slower than green Norway maple |
| Foliage | Deep maroon to purple-black all season; little fall color change |
| Flowers | Small maroon-yellow clusters in early spring before leaves |
| Light | Full sun for best color |
| Soil | Adaptable; tolerates clay, compaction and a wide pH range |
| Lifespan | Often several decades, shorter under stress or with root problems |
The Pros
- Consistent color: Few large trees hold purple foliage through summer heat as reliably. Many purple-leaf trees fade to bronze-green by August; Crimson King mostly does not.
- Cold hardiness: It survives zone 3 winters, colder than many alternatives.
- Urban toughness: Like other Norway maples, it handles compacted soil, road salt, air pollution and drought better than many native maples.
- Strong form: A dense, rounded crown and generally sturdy branching.
The Concerns
Dense Shade and Shallow Roots
Norway maples cast some of the deepest shade of any common shade tree, and their fibrous roots grow thickly near the surface. Grass usually thins and dies under the canopy, and most perennials struggle. Surface roots can lift sidewalks and driveways and make mowing difficult. If you have this tree, accept that the area under it is a mulched or shade-groundcover zone, not lawn.
Invasiveness
Green Norway maple is one of the most widespread invasive trees in Northeastern and Midwestern forests. Its seedlings tolerate deep shade and crowd out native sugar maples and wildflowers. Crimson King produces winged seeds (samaras) too, and many seedlings revert to green Norway maple. Massachusetts and New Hampshire are among the states that prohibit the sale of Norway maple, and other states list it as invasive. Check your state’s invasive plant list before planting one, and pull seedlings in your beds while they are small.
Disease and Disorders
- Verticillium wilt: A soil-borne fungus that clogs water-conducting tissue. Branches wilt and die, often on one side of the tree, and cut branches show olive-green streaks in the sapwood. There is no cure; keep the tree watered and fed modestly, and prune out dead limbs.
- Girdling roots: Norway maples are prone to roots that wrap around the trunk at or just below the soil line, slowly strangling it. Signs include a trunk that goes straight into the ground with no flare, a thin crown and early fall color on one side.
- Leaf scorch: Brown leaf edges in hot, dry, windy summers, especially on trees with restricted roots.
- Tar spot and anthracnose: Black blotches or brown patches on leaves. Mostly cosmetic; rake and dispose of fallen leaves.
- Frost cracks: Vertical trunk cracks from winter sun on the south or southwest side, more common on thin-barked young trees.
Heat Limits
Crimson King does best in cool northern summers. In zone 7 and the hotter end of zone 6, it often scorches and grows poorly, and it is not a good choice for the South.
How to Care for a Crimson King Maple
Watering
Young trees need a deep soak once a week through their first two to three summers, about 10 to 15 gallons per inch of trunk diameter spread over the root zone. Established trees benefit from a deep watering every couple of weeks during extended droughts, which also helps trees with verticillium wilt hold on. Water slowly under the outer canopy, not just at the trunk.
Mulch
Spread 2 to 3 inches of shredded wood mulch in a wide ring, out to the drip line if possible, keeping it 3 to 6 inches away from the trunk. Never pile mulch against the bark in a volcano; it encourages rot and girdling roots. Mulch is also the best answer to bare ground under a mature tree where grass will not grow.
Fertilizing
Most yard trees do not need regular fertilizer, especially if they sit near a fertilized lawn. Feed only if a soil test shows a deficiency or growth is clearly poor, using a slow-release product in spring. Avoid heavy nitrogen on trees with verticillium wilt, since rapid soft growth can make symptoms worse.
Pruning
Prune in late summer, fall or winter while the tree is dormant. Maples bleed sap heavily if cut in late winter and early spring; it does not harm the tree but is messy. Remove dead, crossing and damaged branches, and on young trees develop a single strong leader with well-spaced scaffold limbs. Avoid topping. Large limbs and work near power lines are a job for a certified arborist.
Checking for Girdling Roots
Pull mulch and soil away from the base and look for the root flare, where the trunk widens into roots. If you find a root wrapped across the trunk, an arborist can often cut it out on younger trees. On mature trees, removing a large girdling root can do more harm than good, so get a professional opinion. When planting a new tree of any kind, set the flare at or just above grade and tease apart circling roots from the container.
When to Call an Arborist
Call a certified arborist if you see large dead limbs, wilting on one side of the crown, cracks or cavities in the trunk, mushrooms at the base, or a lean that has changed. These can signal wilt, root problems or structural decay. An arborist can confirm verticillium with a lab test, assess girdling roots and recommend pruning, cabling or removal. You can compare local tree service quotes for pruning and assessments. If removal is on the table, our tree removal cost guide covers typical prices.
Signs Your Tree Is Declining
Mature Norway maples often decline slowly over several years rather than failing suddenly. Watch for a thinning crown with smaller leaves than usual, dead twigs at branch tips, leaves that scorch or drop early in summer, bark peeling away from dead patches on the trunk, and sprouts emerging from the trunk or base. One symptom alone is not cause for alarm, but several together, especially on a tree over a house, driveway or play area, deserve an arborist’s assessment. Keep a photo of the canopy from the same spot each summer; comparing year to year makes gradual thinning much easier to see.
If the tree must come out, plan the replacement before removal and choose a different species. Verticillium can persist in the soil, so avoid replanting another maple in the same spot if wilt was the cause; resistant choices include honeylocust, oaks, birches and conifers.
Should You Plant a Crimson King Maple?
For most homeowners, the honest answer is no. The tree’s invasiveness, dense shade, surface roots and disease issues outweigh the color, especially when alternatives give purple foliage without those problems. The exceptions are very cold zone 3 sites where few purple trees survive, or a planting strip in a dense city where its toughness counts, and even then check whether your state allows its sale.
Purple-Leaf Alternatives to Crimson King
| Tree | Size | Zones (about) | Notes |
|---|---|---|---|
| ‘Forest Pansy’ redbud (Cercis canadensis) | 20 to 30 ft | 5 to 9 | Native species; heart-shaped purple leaves, pink spring flowers; fades greener in heat |
| Purple smoke tree (Cotinus ‘Royal Purple’ or ‘Grace’) | 10 to 20 ft | 4 to 8 | Shrubby small tree; smoky summer plumes; strong fall color |
| Purple-leaf Japanese maple (Acer palmatum ‘Bloodgood’) | 15 to 20 ft | 5 to 8 | Elegant small tree for part sun; see our Bloodgood care guide |
| Copper or purple beech (Fagus sylvatica ‘Riversii’, ‘Purpurea’) | 50 to 60 ft | 4 to 7 | Large, long-lived, needs space; dark purple foliage |
| Purple-leaf plum (Prunus cerasifera ‘Thundercloud’) | 15 to 25 ft | 5 to 8 | Pink spring flowers; shorter-lived |
| Native red maple (Acer rubrum) | 40 to 60 ft | 3 to 9 | Green summer leaves but brilliant red fall color; the native maple choice |
If what you really want is a large native maple with strong color, red maple is the usual answer; our guide on how to grow a red maple covers site and care, and October Glory vs Red Sunset compares two popular cultivars. For a small purple accent, see our Bloodgood Japanese maple care guide. Pair any of these with shade-tolerant underplantings from our flowers and perennials hub.
Gardening Under an Existing Crimson King
Instead of fighting for lawn, mulch the root zone and add tough dry-shade plants in small pockets of compost rather than tilling or adding deep soil, which damages roots. Good choices include epimedium, hellebores, lilyturf, wild ginger, hostas with extra water, and spring bulbs that flower before the canopy fills in. Water new plantings regularly, because the maple’s roots take most of the moisture.
Frequently Asked Questions
Is Crimson King maple invasive?
It is a cultivar of Norway maple, which is invasive in much of the Northeast and Midwest. Crimson King produces seeds, and many seedlings revert to green Norway maple. Some states, including Massachusetts and New Hampshire, prohibit its sale.
How big does a Crimson King maple get?
Typically about 35 to 50 feet tall and 30 to 40 feet wide at maturity, with a dense, rounded crown. Plant it at least 20 feet from houses and away from sidewalks.
Why is my Crimson King maple dying on one side?
Wilting and dieback on one side often points to verticillium wilt or girdling roots. Have a certified arborist inspect the root flare and test a branch sample.
Why won’t grass grow under my Crimson King maple?
Norway maples cast very dense shade and have thick surface roots that take water and nutrients. Replace lawn under the canopy with mulch and dry-shade groundcovers.
Does Crimson King maple turn red in fall?
Not much. Its leaves stay dark maroon most of the season and may turn brownish or bronze before dropping. For bright fall color, choose a red maple or sugar maple instead.