Heliopsis helianthoides looks to have sharper teeth on the leaf edges than the plant in question - scroll down to second picture here:
http://www.missouriplants.com/...
@Anderwood, can you verify that the stems are square in plant 1 and that I'm not seeing things that aren't there? If they are it would narrow down the possibilities. I don't recall heliopsis being one of the plants that, in addition to the mint family, has square stems.
