Sphenosciadium is a monotypic genus of flowering plants in the carrot family containing the single species Sphenosciadium capitellatum, which is known by the common names ranger's buttons, woollyhead parsnip, and swamp whiteheads. It is native to western North America from Idaho through Nevada and California into Baja California. It grows in moist habitat types, such as creeksides and meadows. This is a perennial herb growing from a tuberous root and producing an erect stem easily exceeding...
