Micronesian Names by Island or Island Groups:  Kesengesil or Ngesngesil (Palau), Masigsig (Marianas Islands), Otuot (Chuuk), Masigsig or Wisolmatenrehwei (Pohnpei), Mahsrihsrihk (Kosrae)

Description: Chromolaena odorata is a large bushy highly invasive, non-native, perennial weedy herb or subshrub now found in Micronesia with long rambling, but not twining branches. The Deltoid-ovate leaves with three nerves (veins) are arranged opposite each other and are flaccid-membranous with a velvet pubescence. The leaves are also acute at the tips, very coarsely toothed with 1-5 teeth on each margin, or entire in youngest leaves.

Distribution: Chromolaena odorata is an alien, aggressive plant in Micronesia, and by the early 1980’s it had been recognized as a troublesome weed that was dominating all pasture areas on the island of Rota, Commonwealth of the Northern Marianas Islands, while it was also becoming widely established on the roadside and vacant land vegetation of Guam, Tinian and Saipan. This nasty weed later arrived in Pohnpei, Kosrae, Palau and Yap and is now a noticeable problem in some areas in those islands. Indeed, it is sometimes regarded as one of the “World's Worst” invaders. Although this weed needs disturbance to become established, it grows in many soil types but prefers those that are well-drained. It does not tolerate shade and thrives in open areas, forming dense stands, which prevent establishment of other species, both due to competition and allelopathic (poisonous) effects on other species. In addition, when dry conditions prevail, unfortunately C. odorata serves as a flashy fuel, which promotes wildland fires. “The seeds have small spines that can adhere to clothes, fur and feathers, especially when these are wet” and this assists in the unwanted spread of this species (Vanderwoude et al. 2005).

Uses: Chromolaena odorata is an aggressive weed has been used as an ornamental plant that has occasionally been encouraged for use in shifting slash-and-burn agriculture to compete with the large sharp bladed grass Imperata cylindrica (alang alang or cogon grass) which is even harder to suppress and bring under control. We have included this species here as a major example of a noxious introduced plant species which can hinder traditional use of plants as well as disrupt and displace native species, especially on remote islands.