After releasing some hostas from their weedy prison, I started cutting back the rest of the crap in that area and discovered this:
I kept nudging the back of my mind and came up with liatris. A blog search reveals that this plant is most likely a liatris spicata, a.k.a. gayfeather, moved to its current location during a remodel of the house.
More than likely I will move it one more time, to the south side of the house. I don't think it bloomed last year - it probably needs more sun and fewer weeds.
Meanwhile, the 'Betty Corning' clematis seemed destined to be prone instead of upright. Despite supporting rebar, the two trellises kept toppling over. Today I secured them to the downspouts at each corner of the den. I have tied 'Betty' to the downspouts before, so I think this should be a safe solution.
I am still amazed at how well the Alberta spruce and two juniper chinensis have done in this location.