Here's what happens when you let your cosmos do whatever they want.
What they want is to take over the universe (hence their name), starting with your yard. This batch is easily eight feet tall and thinks it can cut off all escape by blocking the path between the house and the lilacs to the left.
"What path? I don't see any path," you say. Exactly.
Certainly the bees approve:
Happily, the plants are easy to uproot, so I was able to clear out a bunch. Next year I'll be more careful about thinning the seedlings that come up. I know there will be a lot. I resisted this year because "aw, they're so pretty," but we know where that leads.