Avid horticulturists across the land often get frustrated when attractive, floriferous, versatile, durable, and easy-to-grow plants get sidelined because they have been declared an invasive species.
Ruellia simplex (commonly known as Mexican petunia) was declared a category 1 invasive in 2001 by the Florida Exotic Pest Plant Council, described as “a plant that is altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives” (Source: UF/IFAS Center for Aquatic and Invasive Plants).
It produces copious amounts of seed year-long, which do not require exposure to cold weather (stratification) or mechanical damage (scarification) to germinate. Its excellent garden characteristics such as prolific flower production, and adaptability to varying light, temperature and moisture levels also increase its invasive potential.
Fortunately, recent developments in the field of plant breeding have developed several sterile Ruellia cultivars that have demonstrated low invasive potential in field trials. UF / IFAS researchers have developed the MayanTM series, which includes four distinct new cultivars: ‘MayanTM White’, ‘MayanTM Pink’, ‘MayanTM White’ and’ MayanTM Compact Purple’. They are available to the public through various licensed nurseries.
This spring, UF/IFAS Extension agents were given the opportunity to try MayanTM Series Ruellia at their local offices. I opted to try the ‘MayanTM Compact Purple’ cultivar and so far it has been an excellent landscape plant.
It is shorter than other Ruellia cultivars and has adequate branching throughout so as to not look leggy. It blooms regularly and flowers have a nice, purple hue. It does not mind full morning sun but benefits from afternoon shade, particularly during the hot summer months. So far, it seems like an excellent selection for plant borders or areas where a durable source of color is needed. Additionally, it produces no fruit and very little viable pollen, so it does not have potential to hybridize with naturalized Ruellia simplex populations.
Although this is a sterile selection, it can still multiply by rhizomes. While I have not observed any invasive behavior in ‘MayanTM Compact Purple’, I have just tested it in one location.
For more information consult this article from Florida Foundation Seed Producers and one from Hort Science on the ‘MayanTM Compact Purple’ cultivar.