Yankee weed or dog fennel and also mayweed (Eupatorium capillifolium) is a native herbaceous perennial in the Asteraceae. The flowers are in heads, and the heads are in open panicles with drooping branches. This is different from most species of Eupatorium that have the heads in flat topped corymbs. The flowers have five petals and five stamens, and the pappus is formed of bristles. The disc flowers are perfect and white. The ovary is inferior, and fruit is an achene. It has deeply dissected leaves with segments narrower than one mm. It is wind pollinated rather than animal as most of the other species of Eupatorium. Johnny Appleseed planted this plant during his travels in the early 19th century, believing it to be antimalarial. The consequence was that successive, flourishing crops of the weed spread over the whole country and caused almost as much trouble as the disease it was intended to ward off; and to this day is a bad weed in much of the United States. Reported to be used as a substitute for fennel by some. As a kid, we made spears from the stem of this plant. Quite a bit of this plant on Allen Acres. Caterpillars of salt Marsh Moth or Acrea Moth (Estigmene acrea) and Dichomeris aglaia (no common name) are reported to use the leaves of this species. An interesting situation with the scarlet-Bodied Wasp Moth (Cosmosoma myrodora) that uses this plant’s chemicals to protect it from predators. Details in this article: https://www.sciencedaily.com/releases/2000/12/001228091049.htm