What should I plant between my neighbors driveway and mine to create a divide?

Over the summer I pulled out some overgrown bushes that used to be between my neighbors driveway and mine. I'm looking to redo the entire section this spring, but I'm not sure what I should put here. I'm in zone 6a. My property is about 4 feet of this grass here (although I've spoken to the neighbors and they've said they don't care if I cross over into their yard)

My mom suggested some emerald green arborvitaes, and I like the idea, but I worry they'd be much to large for the area when they mature.