Survey and analysis of exotic weeds in China

One hundred and eight species of exotic weeds belonging to 23 families were identified and recorded in China through investigation and referring to the related literatures. Among the exotic weeds originating from various regions in the world, those originated from America accounted for 60%. Concerning the introduction ways, 58% of the exotic weeds were introduced as useful plants, while the others were introduced accidentally in accompany with transportation, imports of agricultural products, etc. The analysis of introduction time indicated that the exotic weeds have been introduced since ancient times, and exotic weeds augmented as the international exchanges grew. The distribution of the exotic weeds in China was governed by the integration of the inherent ecological adaptability of the weeds, their spread capability and the human spread activities.