Pond being taken over by Mimosa

If you look carefully you'll see them everywhere. This pond is only 4 years old and those mimosa moved in since it was dug out.

Easier to see in bloom but I was out taking pictures today so I through this in.

That's typical behavior of this species (and others) that will move into disturbed grounds. Henceforth, rapid and copious seed production with movement of said seed on soil, wind, water, and wildlife allows these pests to exploit every opportunity that goes untended.