Eupatorium capillifolium

Eupatorium capillifolium, or dog fennel (also written "dogfennel"), is a North American perennial herbaceous plant in the family Asteraceae, native to the eastern and south-central United States. It is generally between 50 cm and 2 meters tall with several stems that fork from a substantial base. The stems and base are covered in leaves so dissected that they resemble branching green threads coming out of the stem in fractal patterns. When crushed, the leaves have a sour odor similar to dill pickles. The flowers have a subtle floral odor....read more on Wikipedia.