Eastern Baccharis (Baccharis halimifolia)

All pictures taken on Boardwalk Trial of Bombay Hook NWR, DE
Top left: female flowers in September
Top right: male flowers in September
Bottom left: young leaves are toothed or lobed near the base
Bottom right: older leaves are not toothed near the base but instead often show one or more teeth on either side of the leaf nearer the tip

It's found in coastal areas and can live under a variety of growing conditions. Most often seen as a shrub, but can grow to be a small tree. Male and female flowers grow on separate trees.

http://plants.usda.gov/core/profile?symbol=BAHA&photoID=baha_010_avp.jpg#

http://www.carolinanature.com/trees/baha.html