Abstract
Based on research of ruderal vegetation in the Horná Orava region in the 1980s and in 2005-2007, a list of neophytes was compiled. Thirty-three species of neophytes have been found, representing 6% of the overall flora. The geographical origin, family, life-history, life-form and status of invasion of these species were assessed. The biggest proportion of the species was of North American origin (49%), therophytes (49%) and members of the family Asteraceae (38%). Most of the neophytes are garden "escapees" and only few of them may be considered to be of potential hazard to the studied region, most particularly Fallopia japonica, Impatiens glandulifera and Solidago canadensis. Types of plant communities, where particular neophytes were found, and the foci of their distribution were evaluated as well. Neophytes are most abundant in communities of the class Galio-Urticetea, and especially of the alliance Senecionion fluviatilis. Comparing older and present data, trends in the progression of non-indigenous species in the Horná Orava region were predicted. It is apparent that the number of localities of invasive species is increasing and even other species that in the literature from the other regions are mentioned as invasive tend to spread through the area.