Native to Central America, the white-flowering weed was recently found growing in the Maasai-Mara National Reserve (see map) during a survey by the African branch of the Centre for Agricultural Bioscience International Africa (CABI), based in Nairobi, and the International Union for the Conservation of Nature (IUCN).

By producing chemicals that inhibit the growth of other plants, the alien plant can dominate whole landscapes—especially those already in bad shape due to human land use, according to Arne Witt, invasive-species coordinator for CABI.

During the annual migration of wildebeests, more than a million animals follow a circular path through Tanzania's Serengeti (see