Mexican Petunia (Ruellia simplex) is a fast-growing, evergreen, perennial shrub (often treated as an annual in cooler climates) known for its lavender-blue, trumpet-shaped flowers and tough, drought-tolerant nature. It thrives in full sun, growing 2–4 feet tall. Warning: Highly invasive in Florida and the southeastern U.S.; manage via container planting or deadheading.