I would go with Bugbane...Cimicifuga racemosa. The purple variety. I love this plant and have grown many of them. This is not Penstemon from what I see in your photograph. Shoot, they've change the name of the genus on this plant. It is now Actaea. Change is constant I guess.
By the way, this is one wonderful plant to have...I've grown these in dire environments and they always look nursery fresh and add so much to the composition of a plant bed. Hardy and I would add at least 3 or 5 more to make a big bunch...with a couple placed in another bed to tie this color and texture into your landscape.
I have to say this; your fence is rotting. You need to remove the soil at least 2 inches below the bottom of your fence. Or replace in the next few years. Fix it now and I think it will last another decade or so...
images of bugbane