Three species of Miconia have been found in Australia. M. calvescens is a small tree, which grows up to 15 m tall. It has large leaves that have iridescent purple undersides. M. nervosa and M. racemosa are both shrubs that grow up to 3 m tall. The seeds of these three species are contained in small black-purple or brown fruit that are dispersed primarily by birds. All three species are a significant threat to Australia's rainforests.
Miconias also have the potential to degrade crop, plantation and pasture areas. Birds are attracted to the fruit, which can be spread large distances from the parent tree. Seeds can persist in the soil for more than eight years.
Gardeners value the attractive large, purple leaves of M. calvescens and have spread it as a garden ornamental. M. calvescens has become a major weed in the Society Islands (which includes Tahiti), the Hawaiian Islands and other Pacific islands. In the Hawaiian Islands, this plant is known as the ^^purple plague^^; and it is considered the greatest plant threat to the remaining wet forest ecosystems on the islands.
In Tahiti, M. calvescens has become established over 65% of the island (70 000 hectares) in dense stands, with up to 880 trees per hectare.