Escaped ornamental plants on Lucavsala Island, Latvia
Eight ornamental perennial garden plant species are recorded as garden escapees on Lucavsala Island (Latvia) following a botanical survey carried out in 2016. Lucavsala Island is located on the Daugava river in Riga.
Achillea ptarmica (Asteraceae) is native to Europe – the northern part of Spain and Italy, southwestern Romania and southern Russia, where it grows mainly in damp meadows. On Lucavsala Island, a patch of plants (1 m2 in size) was found in an abandoned family garden.
Artemisia ludoviciana (Asteraceae) is a perennial rhizomatous species up to 1 m tall and native to North America. In Belgium and the United Kingdom, the species is recorded as a garden escapee. In Latvia, the use of the species as an ornamental species is not common though it would be well adapted to the sandy soils of the coastal areas of Latvia. A. ludoviciana is recorded on Lucavsala Island growing on non- cultivated land
Asclepias syriaca (Asclepiadaceae) is a fast-growing perennial species native to North America. The species has invaded extensive areas within the EPPO region resulting in dense stands that can outcompete native plant species. It is regulated in the EU and is included in (EU) Regulation 1143/2014 as a species of Union concern. In Lucavsala, a thicket of flourishing plants occupying a 30 m2 area was found in an abandoned family garden. A large quantity of new shoots was observed but no new seedlings could be found in neighbouring areas. This species has the potential to become locally established and, thus, should be included in the group of new casual alien species in Latvia.
Campanula lactiflora (Campanulaceae) can grow up to 150 cm tall. The species is native to Europe, the Caucasus and Turkey. In Latvia, the species has been available in the horticultural trade since 2011. Three small populations of the species were recorded growing on Lucavsala island in an abandoned garden invaded by vegetation.
Heliopsis helianthoides (Asteraceae) is native to North America and has been cultivated for ornamental purposes within the EPPO region. During the botanical survey, the species was commonly observed to have spread from initally planted areas and to be producing seed in these new locations.
Lathyrus latifolius (Fabaceae) is native to Central and Southern Europe and North Africa. Two populations were recorded on Lucavsala island (0.5 km apart) where the populations consisted of flowering individuals. The authors recommend this species is considered a casual alien in Latvia.
Phlox paniculata (Polemoniaceae) is native to North America and can grow up to 2 m tall. On Lucavsala Island, P. paniculata was found in an abandoned garden. Five P. paniculata plants of different ages, all with flowers, were scattered amongst vegetation dominated by Solidago canadensis and Aegopodium podagraria, and occupied in total an area of about 1 m2.
Rudbeckia hirta (Asteraceae) is native to North America and can grow up to 1 m tall. It is cultivated for ornamental purposes in the EPPO region and is naturalised in ruderal habitats in Central Europe. On Lucavsala island, approximately 30 flowering individuals were found, and the authors recommend this species is considered a casual alien in Latvia.
Sources
Naburga I, Evarts-Bunders P (2019) Status of some escaped ornament perennials in the flora of Latvia. Botanica 25, 131-144