Identify this weed/herb?
The plant pictured grows in dry upland pasture in NE Iowa along the Mississippi River. I've only seen it here and not further north. Livestock don't seem to touch it. It has light green parsley like leaves and grows about 3 ft. tall. Dies back to about 1 ft. in winter. The crushed leaves are extremely aromatic and remind me of something I can't quite remember--sort of like a spicy chamomile. The photo was taken a few days ago and show remaining winter foliage and the weathered blossom tops. I have yet to see it in full bloom just having moved here. Thanks for looking. See photo.