How do I get cottonwood fluff off my window screens?
You cannot dissolve it, because it is fiber. Cotton has to be physically lifted out of the mesh, and the way most people attempt it — brushing the screen while it is still in the window — actively makes it worse by felting the fiber deeper into the weave. Screens have to come off the frame and be washed flat. The second half of the answer is timing: cleaning during the cotton drop is money spent on work that gets undone within a week. In cottonwood country the appointment that holds is early July, after the trees finish.
When it happens: Late May through June, with the drop lasting two to four weeks.
Can it be fixed?
Usually removable
Yes, completely, provided screens come off the frame. Laid flat and washed with water and a soft brush working from the outside face, cotton releases easily. Left in place and brushed, it compresses into the weave and eventually needs the screen rescreened to look right again. Tracks and weep holes need physical clearing, not rinsing — flushing with water pushes fiber deeper into the weep channel and can block it more thoroughly than before.
Female cottonwoods release seed encased in cotton fiber to catch the wind. In river-corridor communities the trees are large, mature, and numerous, and the drop is measured in weeks rather than days.
The fiber is fine, light, and slightly hooked, which is what makes it cling to mesh rather than blowing through it.
Screen mesh is an ideal trap: an open weave that catches the fiber and holds it. Once seated, mechanical agitation from the outside pushes it further in rather than out.
Cotton in weep holes is the consequential part. Those slots at the bottom of a window frame exist to drain water out of the frame. Blocked, they hold water against the sash — through an entire winter — which is how frames rot and seals fail.
In Colorado, cottonwoods survive along the South Platte, Poudre, Big Thompson, and St. Vrain corridors. In New Mexico they survive because of the acequia irrigation system, which is why the bosque villages have far more of them than the surrounding desert.
Screen removal and hand-washing is a standard inclusion in a proper window cleaning rather than an add-on, and in cottonwood markets it is the part of the job carrying the most value. Where mesh has been permanently matted by repeated in-place brushing, rescreening is priced per window and is far cheaper than most homeowners expect.
Very doable. Take screens out and lay them flat on a lawn or a driveway. Rinse from the outside face — the direction the cotton entered — with a garden hose at moderate pressure, then a soft brush if needed, then rinse again. Let them dry fully before reinstalling; damp screens against a frame stain the sill. For tracks and weep holes, use a vacuum crevice tool rather than water. Do not use a pressure washer on screen mesh; it stretches and tears it.
Removing it once is half the job. This is the half that determines whether you pay for it again next year.
This problem is not evenly distributed. These are the markets where local conditions make it common, and why.
Acequia-fed bosque cottonwoods — the heaviest cotton load anywhere we work.
Mature valley cottonwoods along the Rio Grande Boulevard corridor; drifts thick enough to look like snow.
Poudre and Platte corridor trees plus agricultural windbreak plantings.
St. Vrain corridor cottonwoods through the older neighborhoods.
South Platte corridor with mature riparian canopy through established streets.
None, and anyone selling you one is selling you nothing. Cotton is fiber — there is no chemistry to dissolve. It comes out physically, which means screens off the frame and washed flat.
Because they were brushed while still in the window. Brushing from the outside drives the fiber deeper into the weave and compresses it. Screens have to come out and be washed flat, working from the outside face so the fiber exits the way it came in.
Early July. A clean in mid-June is undone within a week. If you want two visits, make them early July and late October — the autumn one matters because it clears weep holes before winter.
It genuinely causes damage when it blocks weep holes. Those slots drain water out of the window frame, and blocked, they hold water against the sash all winter. That is how frames rot and seals fail. Clearing them is the functional part of the job.
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