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CommentsThe flowers of Ruellia spp. (Wild Petunias) have a striking resemblance to the flowers of the cultivated Petunia, which has been introduced from South America and belongs to a different family of plants. However, the flowers of Wild Petunias have less diversity of color. There are several Ruellia spp. in Illinois; some of these are restricted to the southern third of the state. Smooth Wild Petunia is the least hairy of these species as its foliage is hairless or sparingly hairy; only its sepals are reliably hairy. The species Ruellia humilis (Hairy Wild Petunia) is a prairie wildflower that prefers sunny dry habitats. It is a shorter and much hairier plant. Two woodland species, Ruellia caroliniensis (Carolina Wild Petunia) and Ruellia pedunculata (Stalked Wild Petunia), also have hairier foliage and their sepals are linear (less than 1/8" across). Smooth Wild Petunia has lanceolate sepals that exceed 1/8" across. Often, its nearly sessile flowers are partially hidden by the foliage.