Silphium perfoliatum var. perfoliatum  
Family: Asteraceae
cup-plant
Silphium perfoliatum var. perfoliatum image
Merel R. Black  
Etymology: Silphium: old Greek generic name referring to resinous juice
Plants: erect, perennial, 3'-8' tall forb; stems square in X-section, mostly smooth
Leaves: opposite, strongly toothed, upper and lower leaves about the same size, surrounding the stem to form a cup
Flowers: head 1 3/4"- 2 3/4" wide with 16-35 (usually 21 or 34) yellow rays 1/2"-1 1/2" long, disk 1/2"-1" wide; inflorescence of several heads in an open, branched cluster; blooms July-Sept.
Fruits: dry seed with no fluffy pappus
Habitat: full to partial sun; wet to moderate moisture; prairies, woods, streambanks; in sandy, loamy soil
Conservation Status: Native
Silphium perfoliatum var. perfoliatum image
Matthew L. Wagner  
Silphium perfoliatum var. perfoliatum image
Paul Drobot  
Silphium perfoliatum var. perfoliatum image
Matthew L. Wagner  
Silphium perfoliatum var. perfoliatum image
John M. Schoeneker