Artemisia princeps L. (Asteraceae), an overlooked invasive Far Eastern weed in Western Europe

Artemisia princeps, originally native to eastern Asia (China, Japan, and Korea), has been present since at least two decades in several localities in Belgium and the Netherlands. It is in many respects intermediate between native A. vulgaris and introduced A. verlotiorum and, as a result, passed unnoticed for quite a long time. Diagnostic features of these three species as well as of A. × wurzellii (a hybrid of A. vulgaris × A. verlotiorum parentage) are thoroughly discussed and illustrated. A. princeps produces – in contrast with A. verlotiorum – viable seed in Western Europe. Hence, it is able to reproduce both clonally and sexually and is potentially a bigger threat to native biodiversity than A. verlotiorum. Most of the large populations of the latter in the study area turned out to belong to A. princeps instead. Genuine A. verlotiorum appears to be – at least at present – at the edge of the species’ climatic range in Belgium and the Netherlands. Compared with A. princeps it is much more widely distributed in an increasing number of localities in both countries, but usually occurs in rather discrete populations.