Status of Some Escaped Ornament Perennials in the Flora of Latvia

Abstract This paper introduces eight ornamental perennial garden escapees that were recorded by the authors of this article on Lucavsala Island, Riga (Latvia) in 2016. Our data on Achillea ptarmica cv. ‘Boule de Neige’, Artemisia ludoviciana, Asclepias syriaca, Campanula lactiflora, Heliopsis helianthoides, Lathyrus latifolius, Phlox paniculata and Rudbeckia hirta contribute to the knowledge about the occurrence of these taxa in wild. All these species are also growing in the collection of ornamental perennials in the Botanical Garden of the University of Latvia. A review of these species in Latvian herbarium collections has been conducted. Five species, Heliopsis helianthoides, Artemisia ludoviciana, Campanula lactiflora, Lathyrus latifolius, Phlox paniculata, were observed for the first time outside cultivation forming relatively stable, reproducing populations. Two species, Achillea ptarmica multiplex cultivar and Rudbeckia hirta, were previously observed in seminatural habitats and, thus, considered as casual aliens at the naturalization stage. One of the species, Asclepias syriaca, was considered a new to Latvia casual alien species with high potential of invasiveness.