Effects of extracts from various parts of invasive species on the germination and growth of native grassland plant species.

Allelopathy is an important factor influencing whether an invasive plant species can become successfully established in a new range through disrupting the germination and growth of native plant species. Goldenrods ( species) are one of the most widespread invasive taxa in Central Europe of North American origin. Owing to their high environmental impact and wide distribution range, invasive species should be controlled in Europe, and the areas invaded by them should be restored. Numerous studies have reported the allelopathic effects of and , but the results are inconsistent regarding differences in the allelopathic effects of particular plant parts and in the sensitivity to allelopathic effects among native species as well as between the two invasive species themselves. In this study, we aimed to analyse the effect of water extracts from and parts (roots, rhizomes, stems, leaves, and inflorescences) on the germination and initial growth of seedlings of 13 grassland species that typically grow in Central Europe. The tested grassland species differed in susceptibility to allelopathy, with the most resistant species being , , and . The inhibitory effect of 10% water extracts from leaves and flowers were stronger than those from rhizomes, roots, and stems without leaves, regardless of the species. Our study results imply that reducing the allelopathic effect of during habitat restoration requires removal of the aboveground parts, including fallen leaves. The allelopathic effects of roots and rhizomes seem to be of secondary importance.