The foliage and tubers of creeping bellflower are edible. If you're desperate enough to eat parsnips, a similar taste, gnosh on this. You might slow down the creep. We recently had a gas pipeline come through west of town. They took out a bunch of endangered cowslips and threatened toadshades, but managed to just miss this patch of bellflower. Probably just as well. They would have scattered the tubers and made it a bigger patch.