I am very used to finding Common Milkweed (A. syriaca), Swamp Milkweed (A. incarnata) and Butterfly Weed (A. tuberosa) in the wild. I think I may have come across what would be a new species for me, Asclepias sullivantii (known as Sullivant's, Prairie or Smooth Milkweed).
I found these plants in a patch along the Georgian Trail, an old rail line now used for hiking and biking. It runs from Collingwood to Meaford along the shore of Georgian Bay (part of Lake Huron - Great Lakes). Some plants were even sprouting in the crushed limestone at the edge of the trail. Most were growing in a very moist new growth woods.
The photo shows the habitat as well as a close up of the very smooth stem. I'm hoping some members may be familiar with this species and can confirm what it is.