looks like mint. does it smell like mint? def not hydrangea.

doesn't smell like mint...it's about three feet tall at the moment, which is tough to tell from such a tight photo.

Could be a Campanula. Appears to have terminal flower buds. Can you post again when it blooms?

Absolutely will. Thanks for your help in the sleuthing process :-)

looks like my adenophera

Could be - that's very similar to some Campanulas.

I was going to guess adenophora as well.
Gary

either would make sense as a design choice by the former owners, since it's in a bed with big purple and white flowering hostas. I will report back when it flowers.

I'll throw in Hyssop (agastache). Here's mine for comparison. I planted it from seed but didn't like it because I was expecting one if the fancier Agastache's. It grew on me eventually. Self seeds and moves itself around quite easily. And mine has a very square stem.

Ding ding ding! We have a winner! The votes for campanulas win! Thanks everyone. I'm glad I didn't pull it this year.

I meant to say adenophora. LOL! Flowers on the brain.