When we purchased land last summer it was overgrown with this plant. They were about five feet tall at the time. We had the field mowed, but were left with toe-catching stalks in a pad of feathery foliage.
what you have here seems to be the common weedy plant Eupatorium capillifolium, in its early leaf stage. It is usually called Dog fennel, and is in the daisy family, Asteraceae. It has very delicate foliage as it gets older. One site for more information is here: http://pfaf.org/user/Plant.aspx?LatinName=Eupatorium+capillifolium and there are many others. It is a perennial, so it will probably continue to come back.
Steve Hill, Botanist, SCNPS