Euphorbia corollata /Spurge Family
This should have been the official flower of the "Womens' Lib" movement! Look closely at the flowers to see the green "superior" ovaries which are above the "petals" on the female flowers instead of below them. The male flowers do not have the ovary. I found this blooming in Oak Ridge in June. Euphorbia species contain phorbol esters in the sap, leaves and stems and are poisonous to sheep, horses, and cattle.
Where seen: Frozen Head SP, University of Tennessee Arboretum, Great Smoky Mountains NP, Warriors' Path SP