In 2007 the 5-acre field where our gravel road meets the tar, about 2,000' from home, was plowed and disked. Next summer it came up 100% goldenrod and thick, probably caught a load of seeds from nearby. (Why would anyone spend money to plant it?) By mid-August they were in full bloom and for the first time in my life I was miserable with allergy - would cough all day then wake up about 2 AM full of mucus and cough for 3/4 hour straight each night, lasted about a week doing that. Same amount of blossoms in 2009 but only very mild reaction and none since, with lots of goldenrod still there.