In previous images it looked as if your plant was in an orange colored plastic planter. Now it appears to be planted in the ground. Am I seeing that correctly? Did you have time to photograph the underside of the leaves, then stem area and the roots?
Since we have no way of knowing the source of the seed...it could have been in the seed pack with the Feverfew or could have been deposited by a bird or whatever, it may not be native to your area.
I'll just take a random guess.
Maybe it's one of the Erigeron plants? One of the Erigeron acris or has the name been changed to Trimorpha acris?
