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It looks like it’s snowing cotton. Will it make your allergies worse?

Here’s why cottonwood trees produce cotton

The University of Wyoming extension explains why cottonwood trees produce cotton that floats away from trees for several weeks in the spring.
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The University of Wyoming extension explains why cottonwood trees produce cotton that floats away from trees for several weeks in the spring.

This story first appeared March 7, 2016, in Bellingham Families magazine.

You know it’s spring in the Northwest when the sky fills with fluffy white tufts of fuzz, floating in the air on the afternoon breeze.

Don’t worry that your allergies are going to flare, it’s just the seasonal mating dance of the cottonwood tree.

Yes, cottonwoods — like many other trees — have male and female versions. Both genders generate flowerlike “catkins” before their heart-shaped leaves appear in spring.

“Those little puffballs are the way by which the seeds are transported and are put out by the females. Males generate pollen,” said John Wesselink of Bellingham, a self-taught student of trees.

“Trees that spread their seeds this way tend to be very prolific seed producers,” said Wesselink, a retired letter carrier who has traveled the United States in a lifelong quest see most of the hundreds of species of trees that are native to the Lower 48 states.

A complex set of variables must coincide for a cottonwood seedling to sprout, Wesselink said. The seed must be pollinated, and the fertile seed must land in a place that will allow it to thrive, snug in a womb of earth.

“It’s reproduction at its finest,” Wesselink said.

COTTONWOOD TREE sky filled with seeds.jpg
Cotton-like puffs, backlit by sunshine, carry cottonwood seeds on a journey from the treetops back to earth near Scudder Pond in Bellingham. The cottonwoods and other trees of the willow family release their seeds in a show that can resemble springtime snow. Staff The Bellingham Herald file

Cottonwoods are fast-growing and highly tolerant of flooding, and are often found streamside or in wetlands. A deciduous tree, they range in height from 60 to nearly 150 feet and can live 75 to 125 years.

Their relatively soft wood is among the favorite meals of beavers, and they’re popular among dozens of species of moths and butterflies, including the viceroy, a monarch look-alike.

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