Short answer
Yes. American sycamore (Platanus occidentalis) and related species, including London planetree and other plane trees, produce round, ball-shaped fruit clusters that hang from the branches on long, thin stalks. They are often called buttonballs or seed balls, and the tree is sometimes nicknamed buttonwood for them. They are not a sign of disease, and they are the tree’s normal way of making seed.
What the balls actually are
Each ball is a dense cluster of hundreds of tiny, one-seeded fruits (achenes), each with a tuft of fine hairs at its base. The balls are typically around an inch or so across, brownish, and slightly bumpy or fuzzy rather than sharp.
Sycamores are monoecious, meaning one tree bears separate male and female flowers. The female flower heads are the ones that ripen into the seed balls. American sycamore usually bears a single ball per stalk, whereas London planetree and some other plane trees often carry two or more in a string.
How the balls change through the year
- Spring: small round flower heads appear along with the new leaves.
- Summer to fall: the female heads mature into green and then brown balls.
- Winter: the balls often hang on the tree well after the leaves drop, which makes them useful for identification. Our guide to identifying a tree by its seeds places them in the “ball-shaped” group.
- Late winter to spring: the balls gradually break apart and release the hairy seeds, which are carried on the wind and sometimes water. Sycamores commonly grow near streams and wet ground, and this suits that habit. See trees for waterlogged and wet soil for other wet-site trees.
Sycamore balls vs sweetgum balls
The two are often confused because both are round and brown. They differ in several ways.
| Feature | Sycamore | Sweetgum |
|---|---|---|
| Texture | Fuzzy or softly bumpy | Hard, woody, spiky |
| How they hang | On long, thin stalks | Fall as hard separate balls with openings |
| Breaks apart? | Yes, disintegrates into fluffy seeds | No, stays hard; seeds drop from small holes |
| Underfoot | Soft, crumbles | Painful to step on, can roll |
| Leaves | Large, broad, maple-like, with mottled peeling bark | Star-shaped leaves, corky ridged twigs |
If the ball crumbles into fluff in your hand, it is a sycamore.
What about spinning seeds
The spinning seeds that twirl down from trees are called samaras, and they are often nicknamed helicopters or whirlybirds. Maples are the most familiar source, and ash trees and others also produce winged seeds. Sycamores do not make them, so if you see helicopters, you are looking at a different tree. If you are dealing with maple seeds, are maple trees messy covers seed cleanup and planting.
Are sycamore seed balls poisonous to dogs
I am not aware of sycamore balls being listed as a toxic plant for dogs. However, “not toxic” does not mean harmless:
- The fine hairs on the seeds may irritate the nose, eyes, and mouth.
- Chewing or swallowing a lot of plant material can upset a dog’s stomach, and hard pieces could, in some cases, cause a blockage.
Sweetgum balls are the harder, spikier ones and are more of a risk for sore paws. If your dog has eaten a large amount, is vomiting, seems uncomfortable, or is coughing or pawing at the face, contact your veterinarian. A vet or a pet poison hotline can give advice for your particular dog.
Cleaning up and handling
- Wear gloves and, if you are sensitive, a dust mask and eye protection when handling or raking broken-up balls. The hairs can irritate skin and airways in some people.
- Rake or blow the balls up before they break apart and spread fluff, if you want to limit mess.
- Seeds that land on moist soil can sprout, so clear them from beds if you do not want seedlings.
- The balls are fine to add to compost in small amounts, though they break down slowly.
Sycamores also shed leaves, bark flakes, and twigs, so they are a messy tree overall. If cleanup bothers you, consider that when choosing a species for a small yard.
Growing a sycamore from seed
If you want to try it, collect balls in late fall or winter, let them dry and break apart, and sow the seed on the surface of moist soil in spring, since they need light and moisture to germinate. Some growers cold-stratify the seed first. Expect many seeds to be infertile. A sycamore is a large tree, so it is best suited to a wide-open space rather than a small garden. For tree-type background, see our guide to deciduous vs coniferous trees.