I remember reading somewhere that "Dortmund" self-seeds very easily, but that most of the seedlings resemble the mother plant. This certainly was the case for me - The "Dortmund" I grew long ago has died, but I found a seedling next to it, which I gave to a friend. (NO, it was NOT a sucker.)

At least a decade later, that seedling is growing over her rose arbor and is HUGE. I don't see any difference between what I call "Dortmund's Daughter" and her mom. I'lll have to check it more closely!