Last summer I turned over the dirt in my flower bed and planted some bulbs as well as some seeds from my Rose of Sharon, purple coneflower, and Aster. Early this spring cat-mint randomly popped up along with this mystery plant?  Its grown in size, but has no flowers..Any insights as to what this is, and if it's something I should get rid of quick? I included a photo of it as a baby back in March, and a recent photo with a closeup. I'm in zone 6B and this year we had an early spring with many days with temperatures in the 60's.