About 40 years ago, apparently, cities decided to resolve the problem of seeds and fruit falling from public trees by planting only male trees. Male trees don't produce seeds, and don't bear fruit.
They do, however, produce pollen. Massive amounts of pollen.
So now, unlike in the wild, where the plant population runs about 50/50, cities run nearly 100% male trees. So we now have higher pollen counts in some cities than we do in the woods.
Because I am one of those people whose immune system can tell the difference between a plant protien and a foreign disease invader (I am lazy, my immune system is lazy. It doesn't like to work unless it has to), I can laugh at this.
Becky, who lives in misery for about ten months out of the year, is much less amused.