Ruellia humilis aka Fringe Leaf Wild Petunia

Ruellia humilis is a perennial: it lives for more than one year. People call it wild petunia or prairie petunia. It comes from the eastern and central United States. Its family is Acanthaceae, the acanthus family. It is not a true petunia, despite its name. It grows in most of Missouri, but not its far southeastern lowlands. It grows in open woods, glades, prairies, and fields. The soil at these sites is often rather dry.

This plant grows upright to about 2 feet (0.61 metres). It also spreads about 2 feet (0.61 metres) wide. Hairs grow on both the leaves and stems. The olive-green leaves are oblong or shaped like a lance. They reach about 0.33 feet (0.10 metres) in length. Chicago Botanic Garden says they are narrow and bristly, with long stalks. This small plant suits sites where taller plants will not crowd it. In the wild, it grows on ground with gravel and rocks.

The blooms look like petunias, with tubes that flare like bells. Each has five shallow lobes, or sections, with round tips. Blooms can reach about 0.25 feet (0.08 metres) in length. Their hues range from lavender to lilac-blue. They grow alone or in groups at the upper leaf joints. The plant blooms from May through October. Its flowers give it its main show in gardens. Missouri Botanical Garden and Chicago Botanic Garden both report that butterflies visit.

Grow wild petunia in full sun or part shade. It grows in average soil that drains well. Soil can be dry or have a medium amount of moisture. The plant copes with drought and dry ground. It also grows in shallow soil with rocks. These traits suit sunny rock gardens. Both gardens list USDA hardiness zones 4–8 for this plant. Missouri Botanical Garden rates its care needs as medium. It reports no serious insect or disease problems.

Wild petunia suits borders and gardens for native plants. It also fits prairie plantings and less formal wild gardens. Missouri Botanical Garden lists rain gardens as a use, too. The plant still needs soil that drains well. Leave room for its low growth among other plants. Chicago Botanic Garden warns that taller plants can crowd it out. Its small form and long bloom season help it fill these garden roles.