Tree · Platanaceae
American Sycamore
Platanus occidentalis
Give it room and moist ground, and the American sycamore will reward you, growing 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 true giant, and getting to know one is a joy. Native to the eastern United States, it sits among the largest hardwoods on the continent and grows fast, climbing 75 to 100 feet with a crown just as broad. The easiest way to recognize it is the bark, which peels off in jigsaw flakes to leave the upper trunk a smooth, pale, almost ghostly white.
Think of this as a tree for open ground, not tight lots, and you will both be happy. It loves deep, moist, rich soil and takes wet sites, clay, sand, compaction, and even the odd flood in stride. The one thing to plan around is the litter: big leaves, shedding bark, twigs, and round buttonball seed heads drop all year, and the strong surface roots can lift pavement and press on a foundation.
Give it the space it wants and it asks very little of you in return. The main thing to keep an eye on is anthracnose, a spring fungus that browns the fresh leaves in cool, wet weather, and even then you can relax, because the tree leafs out again and rarely carries any lasting harm.
Care
The short version: offer 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, and you will do just fine.
Light
Sycamores are happiest in full sun and grow fastest out in the open, though a bit of partial shade will not trouble them. Crowding and deep shade only encourage powdery mildew, so when in doubt, give the tree plenty of room and light.
Water
This is a tree of stream banks and bottomland, so it leans toward deep, moist ground and even shrugs off wet feet and brief floods. Dry soil shortens its life, which simply means young and establishing trees want watering through any drought. Once it has settled on a good site, it mostly looks after itself, so you can ease up.
Soil
Few trees are as easygoing about soil as this one. It does best in deep, moist, rich earth yet still takes clay, loam, sand, compaction, and high pH in stride. The only thing it truly dislikes is ground that stays bone dry.
Temperature
Hardy across USDA zones 4 through 9, the sycamore handles a wide swing of weather, from roughly -29°F to 100°F (-34°C to 38°C), so the cold alone is rarely your concern. The real seasonal risk is not the chill itself but a cool, wet spring that feeds anthracnose on the new leaves.
Humidity
Outdoors you take whatever humidity the weather offers, and the sycamore goes along with all of it without complaint. Airflow matters more than moisture in the air, because a crowded, shaded canopy is what invites powdery mildew and anthracnose to settle in.
Feeding
A tree in good soil hardly ever needs feeding, so there is no pressure to fuss. Where the ground is poor, a balanced tree fertilizer in spring keeps a young or struggling sycamore vigorous, and that vigor is its best protection against disease.
Pruning
Do your pruning in dormancy, taking out dead, crossing, or anthracnose-infected twigs. Gather the infected leaves and twigs and destroy them rather than leaving them under the tree, where the fungus would simply reinfect next spring's growth.
Repotting
A sycamore belongs in the ground rather than a pot, so it is rarely repotted and you can let that worry go. If you are holding a young one in a nursery container, just pot it up before the roots start circling or slipping out the bottom and before the top growth stalls.
Size & spacing
Plan ahead for a giant, because this tree reaches 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, since the strong surface roots and sheer size leave little room for second thoughts later.
When to plant
This tree likes to be planted while it is sleeping, which makes the timing easy to get right. Set it out in spring or fall during dormancy, look for the inconspicuous flowers in April, and expect the round buttonball seed heads to ripen and scatter from fall all the way 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 worry turns up on the leaves, and on an established tree most of it is more of an eyesore than a real emergency, so try not to panic at the first brown spot. Match the symptom below before you treat, since a fungus and an insect call for very different help. Catch the early signs and you can step in while it still makes a difference.
Browned leaf margins that worsen from one year to the next
When the scorched edges keep returning and spreading season after season, the likely cause is bacterial leaf scorch, a xylem disease carried by sap-feeding insects that a lab test can pin down for you. Since a tree that craves moist ground can show a similar burn during drought, it is worth ruling that out first. There is no cure once the bacterium settles in, but you can still buy the tree many good years by pruning out the worst branches, watering through dry spells, and keeping it strong.
Fix:
- Prune infected branches
- Provide irrigation during drought
- Maintain vigor; antibiotic injections may suppress symptoms
New spring foliage turning brown right as it opens
If the new leaves brown and collapse just as they open, take a breath, because this is almost always sycamore anthracnose, a fungus that wakes up in a cool, wet spring and nips the young shoots before they can settle in. It runs hardest when the air at leaf-out stays under 55°F (13°C) for a couple of weeks, and the repeated twig loss can leave a witches'-broom of stubby growth. You can help the tree recover by raking up and destroying the fallen leaves and infected twigs, pruning away the dead wood, and keeping it watered and fed so it has the strength to push out a fresh, 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
Pale powdery coating settling over the foliage and shoots
A pale, dusty coating on the foliage points to powdery mildew, a fungus that likes crowded, shaded growth and curls the leaves before they drop a little early. Try not to worry, because it looks far worse than it is and seldom troubles a grown tree. Opening the canopy for better airflow and keeping the tree healthy goes a long way, and you only need to reach for sulfur or horticultural oil when a young tree gets hit hard.
Fix:
- Improve air circulation
- Maintain plant vigor
- Apply myclobutanil, propiconazole, sulfur, or horticultural oil if severe
Pale yellow flecks and a bronze tint across the upper leaves
Flip a speckled leaf over and the sycamore lace bug is usually right there, a small lacy-winged insect that feeds on the underside and leaves dark spots below and pale flecks on top. The bronzed look can be unsettling, but rest easy, because it rarely sets back a healthy tree. Let the natural predators do their part, rinse light numbers off with a spray of water, and only step up to insecticidal soap if the infestation grows heavy.
Fix:
- Encourage natural predators
- Wash off light infestations with a water spray
- Use insecticidal soap or imidacloprid when necessary
Toxicity
Here is the reassuring news for a home with pets: the American sycamore is non-toxic to cats, dogs, and horses, and nothing about it will poison wildlife or livestock. The only catch is mechanical rather than chemical. The fine hairs shed from spring leaves and buttonballs can irritate eyes, skin, and lungs, so just cover up when you rake or prune at leaf-out.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax around a curious cat, because the ASPCA lists this tree as non-toxic to them, so a nibble of leaf will not poison your pet. Nothing extra is needed on this front.
Dogs None
A dog can mouth the leaves or bat a fallen seed ball around without any poisoning risk at all. If one gulps down some plant matter, a little passing tummy upset will sort itself out.
Horses None
Horses are in the clear here too, since the ASPCA also marks the tree safe for them. Letting them graze nearby brings no toxic worry.
Rabbits Safe
Neither the leaves nor the bark hold anything poisonous to rabbits, so you can breathe easy. As with any fresh green, offer it a bit at a time so their digestion stays comfortable.
Livestock Safe
Cattle, goats, and sheep are free to browse the foliage without coming to harm, because the tree carries no toxic principles.
Birds Safe
Birds can nest, perch, and peck at the seed heads in perfect safety. The buttonballs are a well-loved winter food and pose no threat to them.
People Safe
There is nothing poisonous about handling or even tasting this tree, so you have no real safety fear there. The single nuisance is mechanical: the fine hairs shed from emerging spring leaves and buttonballs can scratch at eyes, skin, and lungs, so slip on eye protection and a dust mask when you rake or prune 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 a single species, but its anthracnose troubles led nurseries toward the London planetree and its hardier selections. These are the names you are most likely to come across.
London planetree (Platanus × acerifolia / × hispanica)
Born from a cross of American sycamore and Oriental plane, this tree stands up to sycamore anthracnose much better than the native does, which is exactly why cities reach for it so often.
'Bloodgood'
Extension sources point to this London planetree selection for its dependable resistance to anthracnose.
'Liberty'
This London planetree cultivar earns a mention for shrugging off both anthracnose and powdery mildew.
How to propagate
You have two welcoming routes to a new sycamore, seed or a cutting, and one of them is much gentler on a beginner 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 forgiving, low-pressure way in, so it is a lovely place to start. Wait until the buttonballs break apart in fall, then sow without any pretreatment, just remember the seed needs direct light right on the soil surface or it will not sprout. Give it that light and you may be delighted to see a seedling put on 3 to 4 feet (90 to 120 cm) in its very 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 can absolutely work for you, as long as you choose the right wood. Take hardwood cuttings in late winter while the tree rests, or softwood during active growth, and gather them from young, fast-growing stems, since wood from a mature tree just will not root by ordinary means. Allow several weeks for roots to appear and a season or more before the young tree feels truly at home, and do not be discouraged if it takes its time.
Myths
American sycamore will poison a cat or dog that chews it.
You can set this worry aside, because the ASPCA clears the tree for cats, dogs, and horses, so a pet that chews a leaf or a seed ball is not 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 they tend to bother people far more than they bother animals.
American sycamore and London planetree are really just one tree under two names.
They do look alike and share a genus, yet 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 from true sycamore along so many streets.