City Cast

Urban Almanac: Cottonwood Fluff

Sidney Madden
Sidney Madden
Posted on June 8
White fluff coats grass, dirty, and sidewalk

Cottonwood fluff along Winnemac Avenue in Uptown. (Simone Alicea / City Cast Chicago)

White fluff is coating Chicago sidewalks, yards, and window sills. Those are cottonwood seeds, and they’re everywhere.

What’s with all the fluff? Cottonwood trees are masting, which is when a heckuva lot more seeds than usual are produced.

How many seeds are we talking about? One female eastern cottonwood tree can drop almost 50 million seeds, which are covered in thin white hairs that help carry the seeds far. But few actually germinate.

Why so much fluff now? Scientists don’t know exactly, but masting helps trees reproduce. Last year’s warm and dry weather also played a role in triggering the fluff storm.

How are Chicagoans affected? The white fluff might be sticking to your clothes and contributing to allergies as fertilized trees release pollen.

📸 Send your cottonwood fluff pics to, or text them to us at 773-780-0246. We might feature your photos!

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