The fields are full of this stuff in late summer and autumn. It's ironweed [and Queen Anne's lace].
I looove that color.
The butterflies must, too, because they're all over it.
It's a tough plant, with roots to China - hence the common name, Ironweed. The Latin is Vernonia altissima, which pretty much means Vernon's tall stuff. It gets between 4 and 6 feet tall, not quite as tall as Joe Pye weed.
Click the pic for an up close look at the flowers. Notice the old spent flowers at the bottom of the cluster [they're brown], the bloomers in the center and the buds near the top. Each little floret makes a lot of seeds.
A Lot.
Which is why we have ironweed everywhere out here.