Description of the ornamental plant species used in this study.

Species are ordered according to their assessed impact. In the questionnaire, these plant species appeared in a random order.Note: Status of origin for all species is taken from Flora indicativa [42].Assessed impact is based on whether the species is listed on the Black-List, or on the Watch-List [43].*At the time of our study, the use of F. baldschuanica in horticulture was allowed by Swiss authorities, although the species belongs to the Fallopia-complex, that was included in the list of prohibited plant species [46], but not in the Black- or the Watch-List.