Last weekend I visited Cuyahoga Valley National Park and along the Cuyahoga River I came across these conspicuous asters. They were over six feet in height with large and thin alternate leaves and big yellow flowers with drooping ray florets. I keyed them out and found out these are wingstems (Verbesina alternifolia, Asteraceae).
As you can see from the above photo, wingstem gets its name from the fact that the main stem has “wings” on it. The flowers are the real attraction though:
The two flowers above show the typical arrangement of asters; a tight cluster of disc florets surrounded by a showier array of ray florets. The two green objects near the top are the fruit; clusters of wide, flat seeds each with two “spikes” protruding from the top (click the image for more detail).