"gregpresley" expounded:

I'm pretty sure it's campanula rapunculoides - sometimes "affectionately"
called cancer of the garden, because of its invasive tendencies. Be
afraid - be very afraid.....LOL. It's pretty in bloom, but nearly impossible
to eradicate once established - (makes roots like parsnips - even the
tiniest piece of root left remaining after pulling will produce another huge
vigorous healthy plant).

Oh, do I hate that plant, it came into my garden in a pot of peonies,
and you're right, it's impossible to eradicate. Damned thing.....

--
Ann, Gardening in zone 6a
Just south of Boston, MA
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