Mexican petunia (Ruellia simplex) is regarded as an environmental weed in Queensland and is of particular concern in the south-eastern parts of this state, where it was recently ranked among the 200 most invasive plant species. For example, it is listed as a significant non-declared pest plant in Maroochy Shire, an undesirable plant in Caboolture Shire, and a weed of natural bushland and waterways in Gold Coast City., In the last 20 years, Mexican petunia (Ruellia simplex) has gone from being relatively uncommon to being one of the most common and widespread species in Brisbane's waterways. It often forms dense monocultures in wetter sites, particularly along creekbeds and on creekbanks. Such infestations prevent the natural growth and regeneration of native riparian plants (e.g.  Backhousia myrtifolia, Glochidion ferdinandi, Waterhousea floribunda, Carex spp. and Callistemon spp.), and unlike some other riparian weeds it will grow in shady creeks.