There is a fellow in the Houston area of Texas who is teaching on-site wild plant classes at the Houston Arboretum and other parks and nature preserves in the area. Most people know him as the intrepid adventurer, Merriwether, although at the Arboretum some people know him as Dr. Mark Vorderbruggen.
He also holds classes at the very primitive Old Riley Fuzzel/Peckinpaugh Nature Preserve (located at 1209 Old Riley Fuzzel Road, Spring, Texas 77386) on Saturdays or Sundays whenever three or more people schedule it. Email him at email@example.com to set up a session. Maximum group size is 16 people, classes last a bit over two hours. These classes are free of charge but donations are gratefully accepted.
He also seems to have a pretty good class survival rate.
Die Fledermaus does not fear such a tiny ad:
Video of all the PDC and ATC (~177 hours) - HD instant view