Tree · Platanaceae
American Sycamore
Platanus occidentalis
Give it room and moist ground, and the American sycamore grows into one of the largest 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 is a giant. Native to the eastern United States, it ranks among the largest hardwoods on the continent and grows fast, reaching 75 to 100 feet with a crown just as wide. You'll know it at a glance by the bark, which flakes away in jigsaw patches to leave the upper trunk a smooth, pale, almost ghostly white.
This is a tree for open ground, not tight lots. It wants deep, moist, rich soil and shrugs off wet sites, clay, sand, compaction, and even occasional flooding. The trade-off is the litter: big leaves, shedding bark, twigs, and round buttonball seed heads come down all year, and the heavy surface roots will buckle pavement and crowd a foundation.
Plant it where it has space and it asks little in return. The main thing to watch is anthracnose, a spring fungus that browns the new leaves in cool, wet weather, though the tree leafs out again and rarely suffers lasting harm.
Care
The short version: full sun and deep, moist, rich soil, with plenty of room for a tree that tops 75 feet. Water young trees through any drought, prune in dormancy, and rake up the leaf litter to keep anthracnose in check.
Light
Sycamores want full sun and grow fastest in the open, though they'll take some partial shade. Crowding and heavy shade only invite powdery mildew, so give the tree room and light.
Water
This is a tree of stream banks and bottomland, so it likes deep, moist ground and even handles wet feet and short floods. Dry soil cuts its life short, which means young and establishing trees need watering through any drought. A settled tree on a good site mostly fends for itself.
Soil
Few trees are less fussy about soil. It thrives in deep, moist, rich earth but tolerates clay, loam, sand, compaction, and high pH without complaint. What it can't abide is ground that stays bone dry.
Temperature
Hardy across USDA zones 4 through 9, the sycamore takes a wide swing of weather, from about -29°F to 100°F (-34°C to 38°C). The real cold-weather risk isn't the tree itself but a cool, wet spring that feeds anthracnose on the new leaves.
Humidity
Outdoor humidity is whatever the weather brings, and the sycamore copes with all of it. Airflow matters more than moisture in the air, since a crowded, shaded canopy is what lets powdery mildew and anthracnose settle in.
Feeding
A tree in good soil rarely needs feeding at all. Where the ground is poor, a balanced tree fertilizer in spring keeps a young or struggling sycamore vigorous, and vigor is its best defense against disease.
Pruning
Prune in dormancy, taking out dead, crossing, or anthracnose-infected twigs. Carry the infected leaves and twigs off and destroy them rather than leaving them under the tree, where the fungus would just reinfect next spring's growth.
Repotting
A sycamore belongs in the ground, not a pot, so it's rarely repotted. If you're holding a young one in a nursery container, move it up before the roots start circling or escaping the bottom and before the top growth stalls.
Size & spacing
Plan for 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 sheer size leave no room for second thoughts.
When to plant
The American sycamore goes in the ground while it sleeps. Plant it in spring or fall during dormancy, watch for the inconspicuous flowers in April, and expect 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
Almost every sycamore complaint shows up on the leaves, and most of it is more eyesore than emergency on an established tree. Match the symptom below before you reach for a treatment, since the cure for a fungus does nothing for an insect. Read the early signs and you can act while it still counts.
Brown scorched leaf edges that come back worse each year
When the scorch returns and spreads year after year, the cause is usually bacterial leaf scorch, a xylem disease carried by sap-feeding insects that a lab test can confirm. Drought on a tree that wants moist ground brings on a similar burn, so rule that out first. There is no cure once the bacterium takes hold, but pruning the worst branches, watering through dry spells, and keeping the tree strong buys it years.
Fix:
- Prune infected branches
- Provide irrigation during drought
- Maintain vigor; antibiotic injections may suppress symptoms
Spring leaves browning and dying as they unfurl
This is sycamore anthracnose, a fungus that flares up in a cool, wet spring and kills new shoots almost as fast as they open. The damage runs worst when temperatures at leaf-out hang below 55°F (13°C) for a couple of weeks, and repeated twig killing leaves a witches'-broom of stubby growth. Rake up and destroy the fallen leaves and infected twigs, prune out the dead wood, and keep the tree well watered and fed so it can push a healthy 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
Dusty white film on the leaves and new twigs
That powdery coating is powdery mildew, a fungus that settles on crowded, shaded growth and twists the leaves before they drop early. It looks worse than it is and rarely threatens a mature tree. Open the canopy up for better airflow, keep the tree vigorous, and reach for sulfur or horticultural oil only when a young tree gets hit hard.
Fix:
- Improve air circulation
- Maintain plant vigor
- Apply myclobutanil, propiconazole, sulfur, or horticultural oil if severe
Yellow speckling on top of leaves with a bronzed cast
Turn a stippled leaf over and you'll find the sycamore lace bug, a tiny lacy-winged insect that feeds underneath and leaves dark spots and pale flecking above. The damage looks alarming but seldom hurts a healthy tree. Let predators do their work, knock light numbers off with a spray of water, and step up to insecticidal soap only if an infestation runs heavy.
Fix:
- Encourage natural predators
- Wash off light infestations with a water spray
- Use insecticidal soap or imidacloprid when necessary
Toxicity
Good news for a household with pets: the American sycamore is non-toxic to cats, dogs, and horses, and nothing about it will poison wildlife or livestock. 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 lists this tree as non-toxic to cats, so a curious nibble won't poison one. No special caution is needed here.
Dogs None
Dogs can chew the leaves or play with a fallen seed ball with no risk of poisoning. Any mild stomach upset from gulping plant matter passes on its own.
Horses None
Horses are safe around this tree, which the ASPCA also clears for them. Grazing near it carries no toxic concern.
Rabbits Safe
Nothing in the leaves or bark is poisonous to rabbits. As with any new green, introduce it slowly so their gut stays settled.
Livestock Safe
Cattle, goats, and sheep can browse the foliage without harm, since the tree holds no toxic principles.
Birds Safe
Birds nest, perch, and pick at the seed heads safely. The buttonballs are a familiar winter food and pose no danger.
People Safe
The tree isn't poisonous to eat or handle. The one real nuisance is mechanical: the fine hairs shed from emerging spring leaves and buttonballs can irritate eyes, skin, and lungs, so wear eye protection and a dust mask when 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 is one species, but its anthracnose troubles pushed nurseries toward the London planetree and its tougher selections. These are the names you'll meet most often.
London planetree (Platanus × acerifolia / × hispanica)
This cross between American sycamore and Oriental plane shrugs off sycamore anthracnose far better than the native tree, which is why cities plant it so widely.
'Bloodgood'
A London planetree selection that extension sources single out for its resistance to anthracnose.
'Liberty'
Another London planetree cultivar, this one reported to fend off both anthracnose and powdery mildew.
How to propagate
You can raise a sycamore from seed or from a cutting, and one of those is far easier than the other.
SeedEasy
Sow in fall after seed balls disperse · Seedlings can grow 36 to 48 inches the first year under good light
Growing from seed is the easy route. Sow in fall once the buttonballs break apart, and skip any pretreatment, because the seed needs direct light on the soil surface to come up at all. Given that light, a seedling can put on 3 to 4 feet (90 to 120 cm) in its first year.
Stem cuttingsModerate
Hardwood cuttings in late winter/dormancy; softwood during active growth · Several weeks to root, then one or more seasons to establish
Cuttings work, but only from the right wood. Take hardwood cuttings in late winter while the tree is dormant, or softwood during active growth, and pull them from young, fast-growing stems, since wood off a mature tree simply won't root by ordinary means. Expect several weeks for roots to form and a season or more before the young tree is truly settled.
Myths
American sycamore is poisonous to dogs and cats.
The ASPCA clears the tree for cats, dogs, and horses alike, so a pet that chews a leaf or a seed ball isn't being poisoned. The only real irritation is mechanical, not toxic -- the fine hairs shed from spring leaves and buttonballs can scratch at skin and airways, and that bothers people far more than animals.
American sycamore and London planetree are the same tree.
They look alike and share a genus, but the London planetree is a hybrid of American sycamore and Oriental plane, not the native species. The hybrid resists sycamore anthracnose far better, which is the main reason it has largely replaced true sycamore along streets.