Ruellia Brittonia, Mexican Petunia Purple Showers a fully established 2 year old plant of this beautiful, drought resistant perennial for zones 8 and above. This plant, also known as Mexican Petunia, is continuously covered with masses of these 1 inch brilliant purple flowers throughout summer, up until the first hard frost. They grow to 30 and can fill in a dry and sunny area in no time at all. This plant does reseed and also forms runners for extra plants. Zones 8 to 11.