Verbena bonariensis or brasiliensis. I can't tell which without seeing seed heads.

On the invasive species "monitor" list for all of the west coast - WA, OR and CA. So yes, could definitely be problematic.

Thanks. I'll be keeping an eye on it. The little seedlings aren't too hard to scuff away with my foot. It's tall and wild at this point, probably 6' tall. I'm thinking it's the bonariensis variety.

On the invasive species "monitor" list for all of the west coast

Unfortunately not in my garden.

Verbena bonariensis survives one season leaving no seedlings for the next one -- and I scatter the seed heads trying for more plants.

Love the number of skippers the plant attracts, but lantana is the replacement.