The adaptation of alien ornamental herbaceous perennials – benefits and risks

The purpose of the study was to evaluate the adaptation of alien ornamental herbaceous perennials offered by the plant market in Latvia and to find out those taxa that tend to become threatening for local flora. Plants represent 290 species belonging to 176 genera hosted by the Botanical Garden of the University of Latvia. The adaptation was determined based on observations of phenological and biological characters in three-year cycle fixing overwintering, resistance against diseases and pests, reproduction, etc. In the result, the species were arranged into four groups: 55% of taxa were well adapted, 37% NDASH average adapted, 6% NDASH very good and 2% poorly adapted species. Very well adapted species are characterized by successful vegetative or generative reproduction and they tend to become garden escapers, naturalize or to be invasive.