Etymology: Silphium: old Greek generic name referring to resinous juice
Plants: erect, perennial, 2'-6' tall forb; stems leafy, cylindrical in X-section
Leaves: mostly opposite but not surrounding the stem, lower and upper leaves about the same size
Flowers: head 2"-3" wide with 16-33 (usually 21 or 34) yellow rays 3/4"-1" long; disk usually 1/2"-1" wide; inflorescence of many heads in large, branched clusters; blooms July-Sept.
Fruits: dry seed with no fluffy pappus
Habitat: full sun; dry, moderate moisture to wet; prairies, meadows; in sandy, loamy soil