Overall status of naturalized plants in Korea.
Until 2001, some 471 plant species belonging to 64 families had been naturalized to Korea Republic. Among them, 20 species were highly abundant everywhere, 8 species were also highly abundant but locally, 63 species were common (moderately abundant) everywhere, and 31 species were common in certain regions locally. One hundred species were rare but observed everywhere with low frequency. The others, 249 species, were rare and observed locally. The 95.8% (451 species) of the total naturalized plants were xeric, which prefer relatively dry soil like pasture, set-aside fields, roadsides and upland fields. Only 4.2% (20 species) of naturalized plants occurred on wet or swamp like watercourses and paddy fields. A large number (189 species) of the naturalized plants were perennial comprising 40.1% of the total 471 species, 140 species (29.7%) were winter annual or biennial, 142 species (30.2%) were annual. The prominent naturalized species in upland crop fields were Amaranthus patulus [Amaranthus cruentus], Erigeron annuus, Senecio vulgaris, Solanum nigrum, Thlaspi arvense, Erigeron canadensis [Conyza canadensis], Avena fatua, Bidens frondosa, Panicum dichotomiflorum, Galinsoga parviflora, Abutilon theophrasti, Chenopodium ficifolium, Amaranthus viridis, Erigeron sumatrensis [Conyza sumatrensis], Galinsoga ciliata and Chenopodium album. Paddy fields, the most popular type of land use for producing staple crop (rice) in Korea Republic, were the habitat of some naturalized plants known as hydrophyte such as Diplachne fusca, Lindernia dubia var. anagallidea, Leptochloa chinensis, Gratiola officinalis, Lindernia attenuata, Catapodium rigidum [Desmazeria rigida], Alopecurus japonicus, Paspalum distichum and Paspalum distichum var. indutum.