Survey and study on naturalization of imported flowers in Shanghai area.
Ten species of imported flowers belonging to 4 families naturalized in Shanghai, China, were identified and recorded. These were Ageratum conyzoides, A. houstonianum, Coreopsis basalis, C. tinctoria, Helenium autumnale, Mirabilis jalapa, Oxalis corymbosa, Pharbitis nil, P. purpurea and Solidago canadensis. Some of which have caused a great extent of damage, but they have been introduced as good species in recent five years. Imported flowers which are becoming harmful weeds are closely related to certain biological characteristics, environmental adaptive capacity, and planting and management practices of flowers.