Solaklı watershed (Trabzon) is a large one with a total of 83.000 hectares area, rising from the North to South, starting from coast to an altitude of 3.3766 m. in the Eastern Karadeniz Region. It has a North-south section feature for the flora of the region (Colchis sector). In the present paper, 141 vascular alien plant taxa distributed in the watershed were determined. Significant amount of the taxa has become invasive alien species for the watershed. As well, the remaining taxa completed their naturalization in the watershed and become a part of the flora. Invasive alien species are one of the most important factors directly or indirectly affect many ecosystem components in their newly introducing areas. They negatively affect both the native flora and whole biological diversity. They may cause deaths and/or significant yield loss in both natural and agricultural plants due to the different pressures in the natural and agricultural areas. It has been determined that all 20 plant taxa which are considered as the most remarkable invasive alien plants in Türkiye, are distributed in the watershed. In the present study, the effects of invasive alien species on plant biodiversity and the control methods that may be applied considering ecological conditions are discussed.
