The peony (Paeonia) was designated as the state flower of Indiana in 1957 (from 1931 to 1957 the zinnia was the state flower). No particular variety or color of peony was designated by the Indiana General Assembly. The Peony flower occurs in single and double forms and is cultivated widely throughout Indiana.

This showy flower blooms in various shades of red, pink, yellow, and white in late spring and early summer. Peonies are also extensively grown as ornamental plants for their very large, often scented flowers.

Native to Asia, southern Europe and western North America, the peony is among the longest-used flowers in ornamental culture. See State Flowers for all 50 states.

Source:

Indiana State Flower: Governor of the state of Indiana

Links:

State Flowers - 50 States List
National Flower