Bits of white fluff float away from a Silver poplar tree (Populus alba) on a warm sunny day in May. Each bit of fluff is attached to one tiny seed . Photo by Sarah Walker.

During a few mild dry days each spring in Moscow, bits of mysterious white fluff float on the warm air, swirl and skitter down the streets to form drifts against the curbs. White fluff carpets green lawns and shines like motes of white dust against blue spring skies.

This “summer snow” is the springtime dispersal of millions of tiny seeds from poplars, cottonwoods, and tree willows—all members of the willow family.

Poplars are the first to release their seeds, then willows, a week or two later (there aren’t many seed-producing cottonwoods in Moscow). Seed-producing female flowers are on separate trees from pollen-producing male flowers. Numerous tiny seeds with their fluff ripen inside capsules, clustered on green catkins that dangle like tassels from the outer branches. When the seeds are ripe, the capsules burst and the fluffy seeds take to the air, making the airborne journey away from the mother plant. The fluffy seeds need warm dry days for floating and wafting, and damp bare soil for sprouting. Poplars, cottonwoods, and willows produce copious amounts of short-lived, minute seeds, very few of which typically sprout.

Silver poplars are scattered through a few Moscow neighborhoods. They look a little like beefy aspen trees. Their bark is dark and rough near the ground but smooth and pale on the upper trunk and branches. Their leaves are blocky and lobed, white and felty underneath. In May, I watched the poplars along Blaine, Almon, and Mabelle as their seeds ripen and the packed capsules explode their fluff—my visual for how the software program Stuffit Expander works.

The species of tree willow that emits lots of fluff in Moscow, European willow (Salix rubens), grows along Paradise Creek at the south edge of town and in Berman Park. They appear to all be female trees. Their bark is dark gray and rough, new twigs brownish-green (not golden), and their leaves are long, narrow and bright shiny green.

People who suffer from allergic reactions to pollen sometimes blame seed-fluff. But the fluff is not pollen. Pollen is related to blooming flowers; fluff is related to seed production, as entertainingly presented in a book about avoiding allergenic plants called Safe Sex in the Garden by Thomas Ogren (at the Moscow Library).

There are years when seed-fluff piles up pretty deep, clogging drains and air vents. It comes inside my friend Sally’s house on her clothes, her feet, her dog, or through her windows and doors. In Pullman, Fire Department Captain Van Ness told me he’s had to put out wildfires started by people being careless with cigarette butts or matches around cottonwood fluff!

The trees that produce our fluff are unpopular in other ways. Widely spreading roots sneak inside broken pipes requiring rescue by Roto-Rooter. Root sprouts might pop up in neighbors’ yards uninvited. Mowing them down year after year leaves a mat of wood where lawn used to be.

Outside of town, European willows grow all around the Palouse, probably planted by farmers to stabilize stream banks. Silver poplars, which are native to Europe, are planted in North America for fast-growing shade. Willows and poplars can reach eight feet in their first year and 30 feet in just a few years. They make good windbreaks. Potlatch Corporation raises hybrid poplars used for pulp in a small plantation along the Clearwater River near Cherrylane.

“Idaho Hybrid Poplar” is grown and sold at University of Idaho Forestry Nursery. It’s a fast-growing lovely shade tree, and doesn’t produce any fluff.

One June afternoon in 1860, Henry David Thoreau watched fluff in Concord Massachusetts: “. . . I noticed the air as high as the roofs full of some kind of down, which at first I mistook for feathers or lint. . . . It rose and fell just like a flight of ephemerae, or like huge white dancing motes, from time to time coming to the earth. Next, I supposed it to be some gauzy, light-winged insect. It was driven by a slight current of air between and over the buildings and went flying in a stream all along the street. . . . This was white-willow down. . .”

People are still taken by surprise when the air fills with summer snow during a perfect fluff week in May or June.

Copyright: Copyright on articles, recipes and images are jointly held by the Moscow Food Co-op and the respective contributors, except were otherwise noted.

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