The single species is Napaea dioica, a tall perennial herbaceous plant, native to central and eastern USA.

[1] Napaea dioica grows 1.5–3 metres (5–10 ft) tall[1] with leaves up to 75 centimetres (30 in) in length.

[2] Napaea dioica is found growing in areas with moist soil in full sun to part shade.

In Minnesota, where it is listed as endangered, it is found growing in alluvial meadows of the Mississippi river and its tributaries; with other large herbaceous perennials such as Heracleum lanatum, Silphium perfoliatum, and Rudbeckia laciniata.

[2] The species is found in east-central Ohio, across central Indiana and the northern half of Illinois to southwestern Wisconsin, southeastern Minnesota and northeastern Iowa.