We came across this plant in a wooded area in northeast Oklahoma on 08/23/14. It is about 4 feet tall. We have not been able to figure out what it is despite the distinctive appearance. Any help would be appreciated.
Yep, otherwise known as milkweed, host plant to monarch butterflies.
Yeah, I'm really wondering what species though....it's obviously a woodland one...I'm thinking maybe: Asclepias amplexicaulis , but that's just a guess.
It does look like Asclepias amplexicaulis. I have only seen that species in open sand prairies but the large leaves would probably allow it to take some shade.
Poke Milkweed, maybe? It grows in the woods around here.
Asclepias exaltata. It does somewhat resemble pokeweed in habit and leaf shape.
Here is a link that might be useful: Asclepias exaltata, Poke Milkweed
Nope, exaltata doesn't appear (USDA..which is fallible) to be native to Arkansas or Oklahoma or Missourri.