It's a seasonal allergy. I'm pretty sure that "cut loose" in this case just means when the time of year comes that the trees naturally start releasing their pollen.

I'm not a botanist by any stretch of the imagination, but I believe that once pollen is on the trees, the wind is the final thing that shakes it loose.

Here's a video showing what I'm talking about: https://www.youtube.com/watch?v=QEYcBnE-IPA