Tree · Platanaceae
American Sycamore
Platanus occidentalis
Hand it room and moist ground, and the American sycamore becomes one of the grandest shade trees in the East.
Full sun
Every 7–14 days
USDA 4–9
75–100 ft · 22.9–30.5 m
Overview
The American sycamore reads as a landmark long before you reach the door. Native to the eastern United States, it stands among the largest hardwoods on the continent and gains height fast, rising 75 to 100 feet with a crown spread to match. From across a property you place it by the bark alone, peeling away in jigsaw patches to leave the upper trunk a pale, almost luminous white that holds the eye through every season.
Picture this as anchor for open ground, not a tight lot. It settles into deep, moist, rich soil and takes wet corners, clay, sand, compaction, and the odd flood in stride, which makes it a natural for the low, damp edge of a larger yard. The cost of that ease is the year-round litter of big leaves, shedding bark, twigs, and round buttonball seed heads, and a heavy surface root system that will lift pavement and press against a foundation, so it earns its keep best with breathing space around it.
Give it that space and it carries the landscape with little fuss. The one thing to keep an eye on is anthracnose, a spring fungus that browns the early leaves through cool, wet weather, though the tree refurnishes its canopy and rarely shows lasting harm by midsummer.
Care
The short version: full sun and deep, moist, rich soil, with a wide margin of room for a tree that tops 75 feet. Carry young trees through any drought, prune while it sleeps, and gather the leaf litter to keep anthracnose in check.
Light
Sycamores ask for full sun and gain the most in the open, though they accept a measure of partial shade. Tucking one into a crowded, shaded pocket only opens the door to powdery mildew, so reserve a bright, generous spot for it.
Water
This is a tree of stream banks and bottomland, drawn to deep, moist ground, untroubled by wet feet and brief floods, which makes it a fit for the damp low ground a lawn struggles to use. Dry soil cuts its life short, so young and establishing trees need water through any drought. A settled tree on a good site mostly looks after itself.
Soil
Few trees are easier to please at ground level. It does best in deep, moist, rich earth yet takes clay, loam, sand, compaction, and high pH without protest. The one thing it will not forgive is ground left bone dry.
Temperature
Hardy across USDA zones 4 through 9, the sycamore weathers a broad swing of conditions, from about -29°F to 100°F (-34°C to 38°C), so it suits properties well outside the mild middle. The genuine cold-season risk is not the tree but a cool, wet spring that wakes anthracnose on the fresh leaves.
Humidity
Out in the open, humidity is simply whatever the weather delivers, and the sycamore takes all of it in stride. Airflow counts for more than moisture in the air, since a crowded, shaded canopy is exactly where powdery mildew and anthracnose move in.
Feeding
A tree on good soil rarely needs feeding at all. Where the ground runs poor, a balanced tree fertilizer in spring keeps a young or struggling sycamore in vigor, and that vigor is its surest defense against disease.
Pruning
Prune in dormancy, taking out dead, crossing, or anthracnose-infected twigs. Gather the infected leaves and twigs and destroy them rather than leaving them to lie under the canopy, where the fungus would only reinfect next spring's growth.
Repotting
A sycamore belongs in open ground, not a container, so it is rarely repotted. While a young one waits in a nursery pot, move it up before the roots begin circling or slipping out the bottom and before the top growth stalls.
Size & spacing
Plan around a giant: this tree runs 75 to 100 feet tall, or 23 to 30 m, with a spread to match. Keep it well clear of pavement, foundations, and small lots, because the strong surface roots and outright scale leave no room to reconsider the placement later.
When to plant
The American sycamore moves into a property while it rests. Set it out in spring or fall during dormancy, look for the inconspicuous flowers in April, and count on the round buttonball seed heads to ripen and scatter from fall straight through the following spring.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring or fall while dormant
- Harvest: Inconspicuous flowers in April; round buttonball seed heads mature and disperse fall through spring
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Nearly every sycamore complaint surfaces on the leaves, and on an established tree most of it reads as eyesore rather than emergency. Pin down the symptom below before reaching for a treatment, since a remedy aimed at a fungus does nothing against an insect. Catch the early signs and you can act while it still shapes the season ahead.
Dry brown leaf borders deepening season after season
A scorch that returns each season and widens its hold usually means bacterial leaf scorch, a xylem disease moved by sap-feeding insects and confirmed with a lab test. A tree built for moist ground will burn in much the same way under drought, so settle that question first. The disease has no cure once it is in, yet cutting back the worst limbs, watering through dry stretches, and keeping the tree strong can win it several more years on the property.
Fix:
- Prune infected branches
- Provide irrigation during drought
- Maintain vigor; antibiotic injections may suppress symptoms
Newly opened spring growth withering to brown
When a sycamore opens to a cool, wet spring and the new growth turns brown almost overnight, sycamore anthracnose is the culprit. The fungus does its worst when temperatures at leaf-out sit below 55°F (13°C) for a couple of weeks, and seasons of repeated twig killing leave the look of stubby witches'-broom in the canopy. Clear away the fallen leaves and infected twigs, take out the dead wood, and keep the tree watered and fed so it can carry a clean second flush.
Fix:
- Rake up and destroy fallen leaves and infected twigs
- Prune out blighted twigs and dead wood
- Maintain vigor with proper watering and fertilization
- Apply a labeled fungicide (chlorothalonil, thiophanate-methyl, or copper) on small trees if springs are wet
A ghostly white dusting across the foliage
A chalky cast over the foliage and young twigs points to powdery mildew, a fungus that takes hold where growth is crowded and shaded and that leaves the leaves twisted before an early drop. The look is more troubling than the threat, and a mature tree shrugs it off. Open the canopy so air moves through it, keep the tree growing strong, and turn to sulfur or horticultural oil only when a young specimen is hit hard.
Fix:
- Improve air circulation
- Maintain plant vigor
- Apply myclobutanil, propiconazole, sulfur, or horticultural oil if severe
A yellow-flecked, bronze-washed look to the foliage
Pale flecking above and a bronzed tone across the canopy trace back to the sycamore lace bug, a small lacy-winged insect that works the leaf undersides and dots them with dark specks. The display reads worse than its toll, and a healthy tree carries the season without trouble. Let resident predators keep numbers down, rinse light feeding off with a spray of water, and move to insecticidal soap only when an infestation turns heavy.
Fix:
- Encourage natural predators
- Wash off light infestations with a water spray
- Use insecticidal soap or imidacloprid when necessary
Toxicity
A reassuring note for a home with pets: the American sycamore is non-toxic to cats, dogs, and horses, and nothing about it poisons wildlife or livestock that share the grounds. The one catch is mechanical, not chemical. The fine hairs shed from spring leaves and buttonballs can irritate eyes, skin, and lungs, so cover up when you rake or prune at leaf-out.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
The ASPCA places this tree on its non-toxic list for cats, so a stray nibble in the yard poses no poisoning risk. There is nothing here that calls for extra caution around a cat.
Dogs None
A dog can mouth the leaves or carry off a fallen seed ball without any danger of poisoning. If one bolts a wad of plant matter, a brief stomach upset sorts itself out.
Horses None
Horses are in the clear around this tree, which the ASPCA also lists as safe for them. A paddock that runs up to it brings no toxic worry.
Rabbits Safe
Neither the leaves nor the bark holds anything poisonous to rabbits. Treat it like any fresh green and offer it gradually so a sensitive gut stays settled.
Livestock Safe
Cattle, goats, and sheep can browse the foliage with no ill effect, as the tree carries no toxic principles.
Birds Safe
Birds perch, nest, and work over the seed heads in perfect safety. The buttonballs are a known winter food and hold no hazard.
People Safe
The tree is safe to handle and harmless if a bit is swallowed. The only true nuisance is physical: the fine hairs cast off by emerging spring leaves and buttonballs can irritate eyes, skin, and lungs, so wear eye protection and a dust mask for raking or pruning at leaf-out.
Not poisonous, but the fine hairs (trichomes) shed from emerging leaves and from the buttonball seed heads can mechanically irritate the eyes, skin, and respiratory tract of people during spring leaf-out; wear eye protection and a dust mask when raking or pruning at that time.
Varieties
True American sycamore stands as a single species, but its run of anthracnose troubles steered nurseries toward the London planetree and its hardier selections. These are the names you will come across most as you shop a tree for the property.
London planetree (Platanus × acerifolia / × hispanica)
A cross of American sycamore and Oriental plane that handles sycamore anthracnose far better than the native, which is why it lines so many city streets.
'Bloodgood'
A London planetree selection that extension sources name for its resistance to anthracnose.
'Liberty'
A further London planetree cultivar, reported to hold off both anthracnose and powdery mildew.
How to propagate
You can bring on a sycamore from seed or from a cutting, and one of those routes is far gentler than the other.
SeedEasy
Sow in fall after seed balls disperse · Seedlings can grow 36 to 48 inches the first year under good light
Seed is the simple path to a new tree. Sow in fall as the buttonballs come apart, and leave out any pretreatment, since the seed needs direct light on the soil surface before it will rise at all. Where that light reaches, a first-year seedling can stretch 3 to 4 feet (90 to 120 cm).
Stem cuttingsModerate
Hardwood cuttings in late winter/dormancy; softwood during active growth · Several weeks to root, then one or more seasons to establish
Cuttings can work, but the wood has to be right. Take hardwood cuttings in late winter while the tree rests, or softwood through the growing season, and draw them from young, fast-growing stems, because wood off a mature tree will not root by any ordinary means. Allow several weeks for roots and a season or more before the young tree is firmly at home.
Myths
American sycamore ranks as a poisonous plant for cats and dogs.
The ASPCA clears the tree for cats, dogs, and horses, so a pet that chews a leaf or a seed ball is in no danger of poisoning. The only real irritation is mechanical, not toxic. The fine hairs cast from spring leaves and buttonballs can scratch at skin and airways, and that bothers people far more than the animals on the property.
London planetree is simply another name for American sycamore.
They share a genus and a strong family resemblance, but the London planetree is a hybrid of American sycamore and Oriental plane rather than the native species itself. The hybrid resists sycamore anthracnose far better, which is the main reason it has taken over the streetscape from true sycamore.