Sorry to be a late responder. I've been off-line for a few days.
Try them, you might like them. I would put them with something you
already dump leaves or mulch over for winter protection, but otherwise you
are are coldest experimenter that I know of! OOps, I mean the
experimenter with the coldest climate...
Are you still collecting penstemon seeds for folks? I have three
small bushes of P. angustifolius which are covered with seeds. I don't
think there was a chance of cross pollination because they bloomed much
earlier than the others nearby.
Are there any bulbs you do grow with Penstemons?
Marguerite: Always seeking articles or tidbits for next issue of 'The Bulb
Garden'