This is Ruellia humilis, also known as Wild Petunia, fringeleaf wild petunia, hairy petunia, and low wild petunia. These plants get about a foot tall and like to live in full or partial shade where they bloom from the middle of Summer until early Fall. This is a larval host plant for the White Peacock, Texan Crescent, Rusty-tipped Page, Common Buckeye, and Malachite butterflies. USDA Hardiness Zones 3 to 9.