Invasive plants are introduced species that can thrive in areas beyond their natural range of dispersal (USDA-NISIC, 2014). They naturalize over large areas, displace native plants, and disrupt natural ecosystems (Ranney, 2004). In Florida, over 1.5 million acres (approximately 600,000 ha) of public conservation lands have been invaded by introduced plant species (Figure 1), and approximately USA$7 million was spent on management and control of invasive upland plants in 2011. In the USA, control costs and production losses due to weeds was estimated at US $30.6 billion per year (Cusack et al., 2009). For example, purple loosestrife (Lythrum salicaria), was introduced from Europe to USA in the early 1800s.
Purple loosestrife is now found in all continental states except Florida (Blossey, 2002) and accounts for USA$50 million per year in control costs and forage losses.
Mexican petunia, Ruellia simplex (previously also known as R. brittoniana, R. coerulea, R. malacosperma, and R. tweediana), was introduced to Florida from Mexico sometime before 1940 (Hupp et al., 2009) and has now naturalized throughout the state, plus six other southern USA states, Puerto Rico, the USA Virgin Islands and Hawaii (USDA-NRCS, 2014). It is considered as a Category I invasive species in Florida because it is altering native plant communities by displacing native species and changing community structures or ecological functions (FLEPPC, 2013). However, there is no evidence that it is hybridizing with native species (Freyre and Tripp, 2014). Sales of R. simplex ‘Purple Showers’ in Florida were ranked third for herbaceous perennials after pentas and lantana (Rick Brown, Riverview Flower Farms, pers. commun.), so a breeding program aiming to develop sterile, non-invasive cultivars was established at the University of Florida in 2007 (Freyre et al., 2012a). This species will be described in more detail in this paper.