Guide

Look closerPlants

Sycamore and London planetree seed balls in winter

November to April

American sycamore and its street-tree cousin, London planetree, keep round, bristly seed balls dangling on long stalks from bare branches through the winter. Through the winter and into spring the balls break apart, and each tiny seed rides the wind on a ring of fine hairs.

Why this time of year

The seed balls ripen in fall and stay on the tree after the leaves drop, so in the bare months they stand out like ornaments. Late winter and early spring is when they come apart and drop seeds.

How to notice it

  1. Look for a big tree with patchy bark that flakes off in plates, showing pale white, gray, and green patches, often near a river or along a wide street or park.
  2. Scan the bare branches for brown balls about 1 inch across, hanging on long, thin stalks.
  3. Count the balls on each stalk: one on its own usually means American sycamore, a pair (now and then three) usually means London planetree.
  4. Check the ground underneath in late winter for fallen or crumbling balls, and pull one apart to see the seeds with their tufts of hairs.

Try this with kids: Find a seed ball on the ground and gently pull it apart. How many fluffy seeds can you count, and can you blow one away?

Sources

  • gobotany.nativeplanttrust.orgNative Plant Trust Go Botany. Native to MA; 'fairly widespread (S-rank: S4)'; habitat floodplains, shores of rivers or lakes, swamps; 'patterned white-gray bark that flakes off to reveal a green inner bark'; 'also widely planted as a majestic street tree'; Platanus hybrida 'carpellate inflorescences paired or rarely solitary or in trios' vs sycamore 'solitary or rarely paired'.
  • plants.sc.egov.usda.govUSDA NRCS plant guide. 'Fruits ripen September-October (-November), usually breaking up and falling from the tree through the winter and into spring'; 'pendulous, ball-shaped fruiting head 2-5 cm in diameter, the individual achenes drifting in the wind if the head breaks up on the tree'; achene 'with a ring of bristles at the base'; London planetree 'fruiting heads 1-2 on each stalk'.
  • dendro.cnre.vt.eduVirginia Tech dendrology. 'A spherical multiple of achenes borne on a 3 to 6 inch stalk'; 'maturing in November, disseminating in late winter'; 'In winter, the persistent fruits resemble Christmas tree ornaments'; bark 'Thin, mottled brown, green, tan and white', 'readily exfoliates'.
  • plantdatabase.uconn.eduUConn plant database, London planetree: fruits 'borne in 2's and 3's change from green to brown in October persist in winter'; 'P. occidentalis has white inner bark, fruit borne singly'.
  • plantdatabase.uconn.eduUConn plant database, American sycamore: 'rounded, tannish brown fruit 1" in diameter fuzzy looking found solitarily showy persist'.

Checked against these sources on October 23, 2026.

In the guide for November, December, January, February, March, April

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