We performed taxonomic reviews and habitat circumstances survey for 41 un-introduced environmentally harmful plants (as designated by the Ministry of Environment, Korea in 2016). For this purpose, we investigated plant specimens from several herbaria and performed a field survey in the southeastern region of the United States. Base on the result, we presented the most comprehensive results of weed risk evaluation and taxonomic description up to now as well as classification keys for 11 species to apply the regulation management of putative invasive alien species – Centaurea maculosa Lam., Centaurea diffusa Lam., Mikania micrantha Kunth. (Asteraceae), Cenchrus echinatus L., Neyraudia reynaudiana (Kunth) Keng ex Hitchcock, Brachiaria mutica (Forsskål) Stapf, Vulpia bromoides (L.) Gray, Lolium persicum Boissier & Hohennacker, Setaria palmifolia (J. Konig) Stapf (Poaceae), Prosopis glandulosa Torr. (Fabaceae), Fallopia baldschuanica (Regel) Hobub. (Polygonaceae).