Stephanophysum longifolium Pohl
Ruellia brevifolia (Pohl) C. EzcurraRuellia graecizans Backer
common wild petunia, red Christmas pride, stephanophysum, tropical wild petunia
Native to South America (i.e. Brazil, Bolivia, Peru, Argentina and Paraguay).
Naturalised in some parts of eastern Australia (i.e. in south-eastern and northern Queensland and in the coastal districts of northern New South Wales).
Also naturalised in Fiji and Hawaii, in the Pacific Ocean, and on La R union and Mauritius, in the Indian Ocean.
Tropical wild petunia (Stephanophysum longifolium) is regarded as a minor environmental weed or "sleeper weed" in Queensland and New South Wales. This species has been widely cultivated as a garden ornamental, and was first recorded as becoming naturalised near Nambour in south-eastern Queensland in 1973.
Tropical wild petunia (Stephanophysum longifolium) invades disturbed areas of rainforests and riparian vegetation. For example, it has recently invaded disturbed rainforest vegetation along the lower Mulgrave River in coastal northern Queensland. For this reason it is listed as an "undesirable plant" in the Wet Tropics World Heritage Area. It is also becoming common in riparian vegetation in Brisbane, in south-eastern Queensland, and is reported to be the dominant understorey plant in shaded areas in the grounds of the Bellingen Hospital grounds, in north-eastern New South Wales.
In Fiji, tropical wild petunia (Stephanophysum longifolium) is sometimes locally frequent as a weed on hillsides, along trails and roadsides, and in coconut plantations. In La R union it is estimated to have invaded approximately 3000 hectares of wet forest vegetation.