Pollen on windows is the yellow film that settles on outside glass, screens and siding while the trees flower, and in Metro Detroit it keeps landing for weeks. We see maple and oak pollen on outside glass from late April into May. You can clean it off any time, but glass washed in the middle of it is coated again within about a week, so the cleaning worth booking comes in late spring, once the drop is done. Until then, a soft cloth, a bucket of mild soapy water and a squeegee keep it under control.
When the pollen comes down
The dates move from year to year, and from one part of the metro to another. Researchers at the University of Michigan School of Public Health tracked oak flowering across Detroit for one spring. Across the area they mapped, peak flowering ran from April 20 to May 13, and the best predictor of the date was how warm the February nights had been. At the regional pollen station, in a cooler area outside the city, the oaks peaked around May 12 and the oak pollen in the air peaked on May 15.
That lines up with what we see on the glass: maples and oaks from late April into May, with the heaviest coat in May.
Pine and cottonwood pollen runs later. Michigan's Department of Environment, Great Lakes, and Energy (EGLE) says pollen from trees like pine and cottonwood turns up in late spring and summer, floating on lakes and settling downwind on everything around, cars included. People have reported it to the agency as yellow paint. EGLE also says wind can carry pollen 90 miles or farther, so the trees in your own yard are only part of the story.
What it does to glass, screens and siding
On glass, pollen starts as loose powder. What we see after that is the problem: dew or a spring shower wets it, it dries back onto the pane as a film, and a dry cloth at that stage only spreads it around.
Screens catch it in the mesh. A screen full of pollen sitting over clean glass undoes the cleaning the first time it rains, which is why the screens come out and get washed whenever we clean the inside. Window tracks collect it too, packed in with dirt and dead insects, and a wet rag over that just makes mud.
On the outside of the house it settles on every edge that faces up: the top of each lap of siding, window trim, porch rails, deck boards and the garage door. The good news is in EGLE's checklist for telling pollen from a spill. Pollen usually won't stain porous material, so on concrete, wood and siding it rinses off. Wet leaves left on a patio in the fall are a different story, because they leave a brown stain that gets harder to lift the longer it sits.
Why washing glass mid-pollen gets it coated again
The trees keep going whether the windows are clean or not. While they're still producing, glass cleaned during the drop carries a new coat within about a week. In the U-M study, the oak peak alone ran across about three weeks, depending on where in the Detroit area the trees stood, and pine pollen carries on into summer.
So if you only want the outside glass cleaned once a year, wait until the drop is done. One cleaning after the pollen does more than two before it, because the second one is cleaning up the same season.
There is one reason to go early. Winter leaves a salt film on storm doors and lower panes that face the street, and that film can come off in March. The pollen will still come after it. Our post on the best time to clean windows in Michigan walks through the whole year, month by month.
How to clean pollen off windows yourself
For a few windows between professional cleanings, this works. It follows the care steps window makers publish for their own glass.
Work in shade or on a cloudy day. Andersen says cleaning in direct sunlight can cause streaks or let the cleaner dry on the glass, and that a cloudy day gives the best results.
Get the loose pollen off dry. Andersen's first step is a dry, soft cloth over the glass and frame to lift dust and debris. A soft brush does the same for frames and sills. Treat screens the same way and brush or vacuum the mesh before it gets wet, or the pollen clogs the weave. Our guide to cleaning window screens has the full method.
Wash with mild soapy water. A bucket with a little dish soap and a soft cloth or sponge is all the glass needs. Andersen calls for mild soapy water.
Dry the glass before it dries itself. Use a squeegee or a soft, clean cloth, as Andersen's steps say. Water left to dry on its own is where the spots come from. Tap and hose water carry dissolved calcium and magnesium, which is how the U.S. Geological Survey defines hard water, and those minerals stay on the glass when the water evaporates.
Keep pressure off the glass. Andersen lists power washers and pressurized cleaning tools among the things that can damage windows. Milgard's care guide goes further and tells owners not to use a power washer or a garden hose on its windows, screens, doors or hardware, and says the wrong tools may void the warranty. Check your own window maker's guide before you aim a hose at the glass.
Second-story glass is where this stops being a weekend job for plenty of people. We clean outside glass with deionized pure water on a water-fed pole, which reaches most second-story glass from the ground. Nothing is dissolved in that water, so it dries on the glass without spots, and the frames get cleaned on the same pass. Everything that comes with a visit is on our residential window cleaning page.
Pollen on siding, decks and the porch
Siding is where the garden hose comes in. CertainTeed, a siding maker, tells owners to clean vinyl siding with a bucket of soapy water, using dish soap or laundry detergent, and a soft-bristle brush, then rinse it thoroughly with a garden hose. It does not recommend power washing vinyl, because that can drive moisture in behind the panels, damage them or discolor them.
Do the siding before the windows, and keep the spray off the glass. Rinse water running down a wall dries on the panes below it. It's the same reason we wash the house first, then clear the gutters, then clean the windows.
Decks, porch floors, patios and the driveway can take a plain rinse. Pollen sits on top of them, and it rinses away. If a wall or a deck is green or black under the yellow, that's algae, and a rinse won't kill it. Our post on house washing explains how a soft wash handles it, and our pressure washing and soft washing page covers concrete and decks.
When to book the spring cleaning
Late spring, after the pollen. That means late May or June. One visit then clears the winter salt film and the spring pollen together, and the glass stays clean into summer.
If you want the house washed too, put both on the same visit. Outside glass runs March through November here and house washing April through November, so both are open by then. The house goes first, then the gutters if they're due, then the windows, so nothing clean gets rinse water or grit on it.
A few places run on their own clock:
[Northville](/window-cleaning/northville): the outside books up in two waves, spring after the pollen and October before the holidays. The spring dates go first.
[Commerce Township](/window-cleaning/commerce-township): lake-facing glass on Commerce, Union and Long lakes keeps catching pine and cottonwood pollen through late spring and into summer, so the water side shows it longer than the street side.
[West Bloomfield](/window-cleaning/west-bloomfield): the mature oaks in West Bloomfield Woods Nature Preserve and the older trees around the lakes put oak pollen on the glass in May. Lake-facing houses here do best on two or three cleanings a year.
If your trees sit close to the house and you're not sure a date is late enough, ask when you get in touch. We'll tell you before you book.
Questions people ask
Why does pollen come back on my windows so fast?
Because the trees are still producing. We see maple and oak pollen on outside glass from late April into May, and pine and cottonwood pollen carries on into summer. Glass cleaned during the drop is coated again within about a week. One cleaning after the pollen is done lasts far longer than several during it.
How do you clean pollen off windows without streaks?
Work in shade, take the loose pollen off with a dry soft cloth, then wash the glass with mild soapy water. Dry it right away with a squeegee or a soft, clean cloth. Streaks come from cleaner or water drying on the pane, and direct sun speeds that up. Leave the pressure washer in the garage.
Will pollen stain siding, decks or concrete?
It shouldn't. Michigan's environmental agency notes that pollen won't stain porous material in most cases, and on siding, wood and concrete it rinses off with water and a soft brush. A brown stain on a deck or patio is more likely from wet leaves, and green or black on a wall is algae. Both need more than a rinse.
Should I book window cleaning before or after pollen season?
After, if you only want one outside cleaning in the spring. Late May or June, once the maples and oaks have finished, gives you glass that stays clean into summer. Going earlier makes sense for a winter salt film you want off in March, and that glass will need another cleaning once the trees are done.
Get a quote
The spring dates after the pollen fill first. Send your address, a rough window count and whether the siding needs washing too through Get a Free Quote, and we'll price it and put you on the schedule for once the trees are done. Glass Guru has been owner-operated in Northville since 2014.
