Juniper Pollen and Your Windows: Why March Glass Looks Yellow

Most people think of pollen as a spring problem. In Central Oregon it starts in winter.

Bend allergist Dr. Adam Williams told the Bend Bulletin that the pollen season here begins in late February or early March when juniper starts to shed, then peaks around mid April as birch, cottonwood, and maple follow.

So the yellow film appearing on your south facing windows in early March is juniper, not spring dust, and it arrives roughly six weeks before anyone expects it.

Why It Sticks

Dry pollen blows off. The problem is the overnight cycle.

Central Oregon nights are cold enough that condensation forms on glass. Pollen sitting on that surface gets damp, then bakes on when the morning sun hits it. Repeat that for a few weeks and you have a bonded layer rather than loose dust.

South and west facing glass takes it worst, because it gets the most sun and therefore the most rapid drying.

Your Screens Are Pollen Filters

This is the part people miss.

A window screen is a mesh, and mesh catches airborne particles. Through pollen season your screens are doing exactly what they are designed to do, which means they load up with it.

You can clean the glass perfectly and the window will still look dull from inside, because you are looking through a screen full of juniper.

Screens have to come out to be washed properly. They cannot be reached from outside, which is why exterior only cleaning does less for you in spring than it does at other times of year. Screens, tracks and sills →

Do Not Clean in March

This is the honest advice, and it costs us work.

If you book a full clean at the end of March, juniper is still shedding and the trees behind it have not started. Your glass will be coated again within two weeks and you will have paid for nothing.

Wait until late April or May, once the season has finished. Then clean once, properly, and it holds.

If the glass genuinely bothers you during the season, rinse it with a hose. Water is free and it takes the loose layer off without you paying for a full service you will need again.

If You Have Allergies

Two practical things.

Washing screens removes an accumulated pollen reservoir sitting in every window opening in your house. If you run windows open in spring, that reservoir is between you and the outside air.

And keeping windows closed on high pollen mornings does more than anything you do to the glass.

What We Recommend

Book your main clean for late April or May. Screens washed, tracks vacuumed, glass done once the season has passed.

Then a second visit in late September or early October, after wildfire smoke has cleared.

Two visits, timed to the two things that actually dirty glass here. That is what most Bend homes need. Residential window cleaning →