Invasion of a Horticultural Plant into Forests: Affects Native Above-Ground Vegetation and Soil Properties.

Horticultural trade is considered the most important pathway for the introduction of non-native plant species. Numerous horticultural plants are spreading from private gardens and public green space into natural habitats and have the potential to alter native biodiversity and ecosystem functioning. We assessed the invasiveness of the horticultural plant subsp. . We documented its spread in semi-natural habitats in the surroundings of Basel, Switzerland, over the past decades. We compared the performance of with that of the native subspecies based on surveys in forests and a pot experiment under standardized conditions. We also assessed whether the two subspecies differentially affect native forest vegetation and various physical, chemical and biological soil properties. The horticultural has tripled its occurrence in forests in the region of Basel in the last four decades. had both a higher growth rate and regeneration capacity than the native subspecies. Furthermore, reduced native plant species richness and changed the species composition of the ground vegetation, in addition to altering several soil properties in deciduous forests. should therefore be considered an invasive taxon.