Add it to your home screen and it opens full screen: no browser bars, one tap away, and everything stays signed in. Free, nothing to download from an app store.
- Tap the Share button in your browser
- Scroll down and choose “Add to Home Screen”
- Open GrowSomeFood from your home screen
- Open your browser’s menu
- Choose “Add to Home screen” or “Install app”
- Open GrowSomeFood from your home screen
Norway Maple
The dense, dark street tree most of us grew up under - and the parent of the purple 'Crimson King'. It shades out lawns, mats the soil with surface roots, and carpets nearby woods with shade-tolerant seedlings. Banned from sale in Massachusetts and New Hampshire.
Norway maple is not poisonous to people and is safe to handle - the milky sap that beads from a broken leaf stalk is the ID test, not a hazard, though it stains. The real risks are practical: shallow surface roots lift sidewalks and foul mowers, and the heavy limbs of old street trees drop in storms. Horses are the one animal caution - wilted leaves of several maple species have caused red-blood-cell damage in horses, so keep prunings and raked leaves out of horse pasture. Do not plant it.
Overview
Norway maple (Acer platanoides) is the tree a great many Americans have without knowing what it is: the tidy, heavy-shading maple planted by the million along streets and driveways from the 1950s onward, and the species behind the familiar purple-leaved “Crimson King.” In much of the Northeast, the upper Midwest, and the Pacific Northwest it is also a recognized invasive species. It leafs out earlier and holds its leaves later than the natives around it, and its canopy is so dense that grass thins to moss and bare dirt underneath while a shallow mat of surface roots takes the water.
What lifts it from “difficult yard tree” to landscape problem is seed. A mature Norway maple sheds thousands of wide-winged samaras every fall, and - unusually - its seedlings germinate and grow in deep shade, so they carpet flower beds, hedge bottoms, and the floor of nearby woodland, taking the place of the sugar maples, oaks, and hickories that would otherwise come up. Massachusetts and New Hampshire prohibit its sale and importation, it appears on invasive-plant lists across the Northeast and the Pacific Northwest, and other states have restricted or are phasing out its sale - check your own state's list before you buy or move one. Nobody is going to make you cut down a healthy tree you already have. This entry is here to help you tell it from a sugar maple, understand what it is doing to the ground beneath it, and decide what comes next.
Quick facts
For identification. Not a growing guide.
- Life cycle
- Perennial, lives about 80 years
- Where it grows
- Full sun · Part sun · Part shade · Shade, well-drained soil
- Height
- 55 ft35 to 75
- Spread
- 45 ft25 to 60
- Cold
- Takes hard frostdamaged below -30°F
- Heat
- Struggles above 100°F
- Self-sows
- Yes. Never let it set seed.
Through the year
How to recognize it in each season.
Early-spring yellow-green bloom (identify)
Apr to May, every year- Recognize it: upright yellow-green flower clusters before the leavesNorway maple flowers early, before or as the leaves open, in upright flat-topped clusters of small yellow-green flowers that give the whole crown a soft chartreuse glow from a block away - noticeably showier and yellower than the small reddish-green tassels of a sugar maple. Red maple blooms earlier still and is red, not yellow-green. A big street maple that looks like it is blooming lime-green in April is almost always Acer platanoides.
Key signs- Upright yellow-green flower clusters before leaf-out
- A chartreuse glow to the whole crown in April
- Neighborhood street trees all blooming at once - a sign of mass planting
Milky sap & the dead zone underneath (identify & control)
May to Sep, every year- The milky-sap test settles itSnap a leaf off at the stalk and watch the broken end. Norway maple oozes MILKY WHITE sap within a few seconds; sugar maple, red maple, and silver maple run clear. Back it up with the leaf shape - Norway maple leaves are broader than long with lobes drawn out to long slender points and only a few coarse teeth, while sugar maple leaves are about as long as broad with rounded notches between the lobes.
- Pull the seedlings every springSeedlings come up by the hundreds in beds, lawn edges, and hedge bottoms, and they germinate in deep shade where most trees cannot. Pull them while the soil is moist and they are under a foot tall, taking the whole taproot - a two-year seedling already resists pulling. Do this every spring and you keep a single tree from seeding a neighborhood; skip a few years and you are cutting saplings instead.
- Look at the ground under the canopyThe signature of a mature Norway maple is bare, dry, root-bound soil beneath it. Its leaves come out early, drop late, and overlap so tightly that little light reaches the ground, and a dense mat of surface roots takes the water. Grass thins to moss and dirt, shrubs sulk, and woodland wildflowers disappear. That dead zone is the reason to plan a replacement rather than keep feeding a losing lawn.
Key signs- Milky white sap from a broken leaf stalk
- Bare, root-matted ground under the canopy
- Seedlings carpeting beds, lawn edges, and nearby woods
Wide-winged samaras & seed rain
Aug to Oct, every year- Samaras spread almost in a straight lineNorway maple keys hang in pairs whose wings spread out nearly flat, close to a 180-degree line, and the seed cases are noticeably flattened. Sugar maple and red maple keys hang in a narrow V, closer to 60-90 degrees. It is the fastest ID at the end of summer, and the wings are what carry the seed - the samaras spin well clear of the canopy on any wind.
- Rake and bag the seed before it germinatesOne mature tree drops thousands of samaras. Rake or blow them off beds, gravel, and lawn edges before spring and put them in yard waste rather than compost, and clear the gutters and downspout beds where they collect and sprout. It will not stop seed already blown into the neighbors' yards or the woods behind you, but it cuts the flush you will otherwise be weeding in May.
Key signs- Paired keys with wings spread nearly flat in a line
- Heavy seed drop onto beds, gravel, and gutters
- Seedlings appearing far from the tree, including inside woodland
Winter form, bark & girdling roots
Nov to Mar, every year- Fat purple buds and fine regular barkIn winter Norway maple carries plump, rounded, blunt buds in opposite pairs, usually dark red-purple to greenish, on stout twigs. Sugar maple buds are slim, sharp-pointed, and brown. The bark is finely and regularly furrowed into shallow interlacing ridges that never plate or peel; older sugar maples break into coarse plates that curl away at the edges.
- Check the trunk flare for girdling rootsNorway maple is notorious for stem-girdling roots - surface roots that circle the trunk and slowly strangle it. Clear the leaves and soil away from the base: a healthy trunk widens into a visible flare where it meets the ground. If the trunk instead goes into the soil straight, like a telephone pole, or a root crosses hard against the bark, the tree is being girdled. That is a slow decline, and one more reason to plan the replacement now.
Key signs- Plump blunt purple-green buds in opposite pairs
- Fine regular interlacing bark ridges (no curling plates)
- A trunk with no visible flare, or roots crossing hard against the bark
Watch out for
5 to know. 2 are high-risk: Deep Shade & Surface Root Mat, Shade-Tolerant Seedling Carpets. 4 are active in September.
Deep Shade & Surface Root MatSeverity High DisordernowThis is the complaint that brings most people to this page - nothing will grow under my maple.
It is not a soil problem and it is not fixable by feeding the lawn.
Bare, dry, root-bound soil under the canopy; turf failing and moss taking over; perennials and shrubs declining year after year within the drip line; surface roots lifting turf, paths, and pavement.
There is no way to lighten the shade or undo the root mat on a mature tree, and cutting surface roots destabilizes it. Manage around it with mulch and shade-tolerant planting outside the drip line, and replace the tree when the time comes.
Do not plant one. Where a tree already stands, do not try to hold turf under it - mulch a wide ring instead, keep new plantings outside the worst of the root mat, and plan a native replacement.
The everyday hazard for the gardener and the core ecological one: Norway maple leafs out early, drops late, and holds a canopy dense enough to starve the ground of light, while a shallow mat of surface roots takes the water and nutrients. Lawns thin to moss and bare dirt, shrubs and perennials sulk and fail, and in woodland the spring wildflower layer disappears entirely.
Shade-Tolerant Seedling CarpetsSeverity High DisordernowThe purple cultivars seed just as freely as the green species; their seedlings mostly come up green, which is why people do not connect the two.
Hundreds of small maple seedlings in beds, gravel, gutters, and hedge bottoms each spring; a woodland understory that is nearly all one kind of maple sapling; green seedlings under a purple-leaved tree.
Hand-pull small seedlings with the taproot. Cut saplings low and treat the fresh stump immediately with a herbicide whose label lists the site, following the label - a plain cut makes them resprout into multi-stemmed clumps that fruit again in a few years.
Never plant one; pull seedlings every spring while they are small and the soil is moist; rake and bag samaras off beds and gravel before winter rather than composting them.
Why it invades rather than merely annoys: a mature tree sheds thousands of wind-borne samaras, and the seedlings germinate and persist in deep shade where native tree seedlings cannot. They build up as a dense carpet under intact forest, so when an old native falls the gap is already filled with Norway maple - and beds, hedge bottoms, and lawn edges fill with them too.
Stem-Girdling RootsSeverity Medium DisordernowCommon enough on this species that a suspiciously post-like trunk on a mature Norway maple is worth uncovering and checking.
A trunk that enters the ground straight, like a post, with no widening flare; a root visibly crossing hard against the bark; a flattened or sunken side to the trunk; thinning or dieback confined to one side of the crown.
A certified arborist can sometimes remove a girdling root before it compresses the trunk, but the operation is risky on a large tree and useless once the trunk is deeply grooved. In that case it becomes a structural risk to assess, and an argument for replacing the tree on your schedule rather than a storm's.
Nothing to prevent on an existing tree beyond keeping mulch and soil off the trunk flare so you can see what is happening; the underlying fix is not planting the species.
Norway maple is unusually prone to stem-girdling roots - surface roots that circle the trunk and slowly compress the tissue that moves water and sugars, causing gradual thinning, one-sided dieback, and eventual failure decades after planting. Trees planted too deep or left in a circling nursery root ball are worst affected.
Verticillium WiltSeverity Medium DiseaseNorway maple is one of the most frequently affected landscape trees, and heat- and drought-stressed trees at the southern edge of its range go down fastest.
A branch-by-branch decline in a mature Norway maple is often this.
One branch, one limb or one side of a plant wilting, yellowing and browning in summer while the rest carries on normally - the lopsided pattern is the tell - and leaves that wilt and then hang on rather than dropping cleanly. Cut into affected wood and look for olive-green, grey or brown streaking along the grain; in a cut vegetable stem it shows as a ring of discolored dots. On vegetables, lower leaves yellow in a wedge from the margin inward, and the plant wilts at midday but recovers overnight in the early stages.
There is no cure and nothing to spray. On a tree or shrub the aim is to keep it alive long enough to compartmentalize the fungus, which many plants manage for years: prune out dead and wilting branches well below the discolored wood, sanitize the pruners between cuts, water deeply through dry spells, mulch, and feed lightly rather than pushing it with a heavy feed. On vegetables, pull and bin affected plants rather than composting them, and move that crop to clean ground or to containers of fresh mix. Do not replant the same species where one has died.
There is no way to sterilize garden soil of it, so prevention is plant choice and plant vigor. Do not replant a susceptible species where one has already died of it. Grasses, conifers, ginkgo, hawthorn, hornbeam, honeylocust, oak and beech do not get it, and many vegetable varieties carry bred-in resistance - the V in a VFN code on the seed packet. Rotate susceptible vegetables on a long cycle and keep them off ground where the disease has shown. Buy clean stock, avoid wounding roots with spades and machinery, and keep woody plants steadily watered, mulched and only lightly fed, because a vigorous plant walls the fungus off far better than a stressed one.
A soil fungus (Verticillium dahliae and relatives) that enters through the roots and grows upward inside the water-conducting tissue, plugging it from within. The plant is not being eaten or rotted, it is being cut off from its own water supply, which is why the signature symptom is one branch or one side wilting and browning while the rest looks perfectly healthy. Cut into affected wood or stem and the tissue is streaked olive-green, grey or brown. The host range is enormous - maples, redbud, olive, tomato, potato, pepper, eggplant, strawberry and many more - and the fungus survives in soil for years as tough resting structures, so infected ground stays infected. Grasses and conifers do not get it.
Tar SpotSeverity Low DiseasenowNorway maple is the main host in North America - the alarming black blotches people photograph in August are almost always on this tree, and they are cosmetic.
Shiny raised black spots (like drops of tar) on the leaves, sometimes with yellow halos, appearing in late summer.
None needed - it's cosmetic; leaf sanitation reduces it over time. Fungicides are not warranted for a shade tree.
Rake and remove or compost fallen leaves in fall to reduce next year's spore load; ensure good airflow.
A fungal disease that makes conspicuous raised black, tar-like spots on maple leaves in late summer - dramatic-looking but essentially harmless to the tree.
Grower tips
Notes from growers, tagged with the zone they grow in. A person reads every post before it appears.
Nobody has posted about Norway Maple yet.
Free account. Your post shows your grower name and zone, never your email.