What is the white fluff floating around in Northern Italy (Lombardy) in Spring?

I was in Northern Italy in the last week of April this year and we couldn't help but notice millions of white fluff continuously floating through the air the whole time. No one seemed interested in this spectacle apart from us. We were in Milan and surrounding towns/villages. Although we did not see them in Verona but it was raining that day.

We figured it was from a tree or plant pollinating but when we asked Italians what this phenomenon was the most we got was that its called 'polline' but nothing about where it comes from.

Which tree does this white fluff come from and is there a specifically large gathering of trees in the Lombardy region that it comes from? I would like to visit in future to see them pollinate at source.

It is quite unusual for me to see literally millions of pieces of white fluff gently float around in the breeze all day long for a week.

Best Answer

It's the seed tufts of a poplar species, specifically Populus nigra:

As this article says:

The tree loves a wet, marshy soil. Which explains why there are so many poplars around Milan and in the Po River plain generally, which is a pretty soggy place. And in Milan, the problem of flying white fluff was truly awful. These pictures are not from Milan but are from that part of the country and give a good sense of the horror of it.

Same article has a photo of how the street looks: