Ambrosia trifida

A common weed of disturbed areas, also sometimes occurring in young forest.

Pseudanthia near Griffy Lake, north of Bloomington, IN, 8/20/03.

A cauline leaf near Griffy Lake, 8/20/03. The cauline leaves are usually trifid, hence the name, but plants often have unlobed leaves when growing in the shade, as this one was.