Spread of alien Impatiens glandulifera along rivers invaded at different times

Invasion of Impatiens glandulifera was reconstructed along rivers in the Czech Republic, central Europe, based on floristic records. The occurrence was assessed along river banks, outside the river banks, and along tributaries downstream from the first records of the species in 1902, 1903, 1978 and 1995, respectively. The following main results were obtained: (a) The species nowadays occupies 77% of the river length in the country. (b) The rivers, investigated in detail, did not differ in the occurrence of the species along the river banks. (c) There were some significant relationships between the penetration of I. glandulifera far from the river banks both in terms of the lateral dimension in the main valley, and upstream along the tributaries, and the time of the first occurrence of the species on the river. (d) It took approximately 20 years from the first occurrence on the main river and the start of spread along the tributaries. The process of invasion is still in progress after about one century and further spread is expected.