Performing a thorough inventory of alien plant species in the southern part of Lithuania, we found twelve alien plant species previously not registered in the country: Aruncus dioicus, Buxus sempervirens, Clematis vitalba, Clematis recta, Colutea arborescens, Erechtites hieraciifolius, Erigeron strigosus, Euphorbia marginata, Genista sagittalis, Lathyrus latifolius, Sempervivum arachnoideum and Silphium perfoliatum. All newly recorded alien species, except Erechtites hieraciifolius and possibly Genista sagittalis, have been introduced intentionally and escaped from cultivation. Ten species currently occur as casuals, whereas Colutea arborescens and Genista sagittalis are locally naturalised. Naturalisation of Buxus sempervirens and Euphorbia marginata in the foreseen future is unlikely in Lithuania, naturalisation of Aruncus dioicus, Sempervivum arachnoideum and Silphium perfoliatum is possible. In contrast, naturalisation of the other five species is expected in the nearest future. Invasion of seven analysed alien species is unlikely in Lithuania, whereas Clematis vitalba, Colutea arborescens, Erechtites hieraciifolius, Erigeron strigosus, Lathyrus latifolius have the potential to become invasive in the country. Therefore, their reproduction and spread should be monitored, and measures for prevention of their invasion should be applied, if necessary.
This paper presents information about ten new alien plant species recorded in Lithuania in the period from 1995 to 2014. These species belong to eight families: Cucurbitaceae (Lagenaria siceraria), Juncaceae (Luzula sylvestris), Lamiaceae (Physostegia virginiana, Sideritis montana), Poaceae (Melica altissima, Miscanthus sacchariflorus), Portulacaceae (Claytonia perfoliata), Scrophulariaceae (Digitalis purpurea), Solanaceae (Datura inoxia) and Zygophyllaceae (Tribulus terestris). Three species (Claytonia perfoliata, Sideritis montana and Tribulus terestris) were introduced accidentally, whereas other seven species were introduced deliberately and later escaped from cultivation. One species, Luzula sylvatica, is ascribed to the group of established aliens, whereas other recorded species are treated as casual. Local establishment of Claytonia perfoliata, Digitalis purpurea and Melica altissima is expected, whereas Miscanthus sacchariflorus can become established and even invasive in the future.
Many woody plant species that originate from various regions of the world have been introduced in other regions or continents and are used in ornamental gardening, silviculture, erosion control, for fruit sources or other purposes. Woody plants selected for introduction usually originate from regions with similar climate conditions; therefore, after certain time lag they start to spread outside places of cultivation, become naturalized or even invasive. In addition to 77 woody alien plant species reported in Lithuania, ten new species were recorded and analysed in this paper. Information on the native and anthropogenic ranges, first record in Lithuania, size of populations, habitats, reproduction and naturalization of Aralia elata, Berberis thunbergii, Caragana frutex, Celastrus orbiculatus, Cornus alba, Cytisus austriacus, Hydrangea arborescens, Pinus strobus, Rhus typhina and Thuja occidentalis is presented. All these species have been introduced intentionally and are used mainly in ornamental gardening. Three of the reported species, Berberis thunbergii, Hydrangea arborescens and Thuja occidentalis, currently are casual species. Remaining seven species were recognized as naturalized in Lithuania, and five of these, i.e. Aralia elata, Celastrus orbiculatus, Cornus alba, Pinus strobus and Rhus typhina as well as Berberis thunbergii, which currently is treated as a casual, have very high or high probability of getting invasive. Constant survey of potential habitats, detection of new escaped alien plants, particularly of trees and shrubs, is the best way to reveal potentially dangerous species and make timely decisions for their control or eradication, if necessary.