Senecio elegans, indigenous along the south coast of the Western and Eastern Cape, is these days commonly photographed in New Zealand and California, posted in iNaturalist.
The prettiest plant becomes bothersome when invading where natural enemies are absent and unable to limit its spread. By the time this happens, the human culprit or culprits who acted on the then "good" idea of introducing the species are long gone.
Very few people intentionally mess up nature where they live but garden escapes do occur. The pretty target plant, so innocuous back home where it knows its place, may usurp territory and disturb an ecology (Manning, 2009; Bean and Johns, 2005; iNaturalist).