Buckeye butterflies Junonia coenia are willing to lay eggs on different host plants, unlike some that will use only one plant, like those that use only a certain species of passion vine. The common element is that the plants that they choose contain a certain glycoside that is a deterrent to predators.
Buckeye nectaring on Tithonia
According to Georgia Wildlife Federation, Buckeye hosts include: Ruellia, Penstemon, Snapdragon, Toadflax (Linaria canadensis), Chelone.
False Foxgloves (Gerardia) Agalinis sp. which bloom in September here are popular fall hosts.
Host plants vary in different areas of the country. Buckeye host plants used in southern Ohio include various figworts, plantains, vervains and acanthus. (Ohio DNR "Common Butterflies & Skippers of Ohio" p.44) -- I frequently see plantains listed as hosts.
An interesting thing about Agalinis is that it is a parasite on the roots of certain trees, including Sweetgum, Sycamore and Slash Pine. I had determined to scatter seeds of Agalinis after they ripen. Knowing that they require a host will determine where I scatter, to increase the chances of good growth. An annual, they are not thought to be a threat except possibly to second year growth in tree plantations.