Mexican Petunia
Mexican petunia is an attractive blue- to purple-flowered perennial that is available at some garden centers. Gardeners have traditionally used Mexican petunia to add height to perennial borders, since it can grow up to three feet tall.
However, Mexican petunia (Ruellia simplex*) has been classified as a highly invasive plant in Florida. This means that it can escape from home gardens and spread into natural areas where it crowds out native species.
You shouldn't plant Mexican petunia in your garden, unless you're able to buy a cultivar like 'Purple Showers' that has been tested and specifically found not to be invasive. There's also a native wild petunia, Ruellia caroliniensis, but it's not as widely available. By making responsible choices and not planting invasive species, you'll help safeguard Florida's natural areas for future generations to enjoy.
(*Note: Mexican petunia's Latin name has changed many times, due to the rules of taxonomy. Suffice it to say: if you're purchasing a Mexican petunia plant, be sure it's either the native caroliniensis or a sterile cultivar. When in doubt, ask the seller.)