Skip to main content
Have a personal or library account? Click to login
Alien trees and shrubs of Latvia – evaluation of current status and invasiveness Cover

Alien trees and shrubs of Latvia – evaluation of current status and invasiveness

Open Access
|Feb 2023

Full Article

Introduction

Human activities on a global scale enable an increasing number of species to colonise regions outside of their native range, establish self-sustaining populations and expand further into natural habitats. This phenomenon is known as biological invasion (Elton, 1958; Nentwig et al., 2018). Some alien species have a considerable negative environmental and socio-economic impact on their newly occupied habitats, requiring large efforts to mitigate this impact (Vilá et al., 2008; 2010; Nentwig et al., 2018).

Exotic species have long been considered valuable and desirable souvenirs imported from distant places (Nutt & Kubjas, 2020). A study of the economic uses of plant species that are invasive in various parts of the world showed that most are ornamentals (Weber, 2003). These species have been introduced for horticultural use by nurseries, botanical gardens, and horticultural enthusiasts (Reichard & White, 2001). Some of the exotic species introduced to Europe, initially planted in botanical gardens and later in parks and as urban greenery, have now become invasive (Stace & Crawley, 2015).

After the introduction of non-native tree and shrub species into Europe, their acclimatization and propagation for landscape gardening began. Alien tree and shrub species were often planted in parks and urban greeneries. In the 17th – early 18th century, mainly non-native berry bushes like Cerasus avium (L.) Moench, Cerasus vulgaris Mill., Cydonia oblonga Mill., Malus domestica Borkh., Ligustrum vulgare L., and other taxa were planted in manor gardens in Latvia (Janelis, 2010). The oldest known tree species introduced as greenery in Latvia is Salix euxina I.V. Belyaeva (syn. S. fragilis L.). The first documented evidence about this species dates from 1791 (Evarts-Bunders, 2005). More information about the introduction of non-native tree and shrub species was published in a catalogue of ornamental trees and shrubs in 1805 (Mauriņš & Zvirgzds, 2006). In the 19th century, many parks and urban greeneries were created in Latvia, which created a demand for a wide assortment of woody plants, and the first nurseries with a large range of trees and shrubs appeared (the most famous nursery business owners in Latvia were Johann Zigra, Karl Wagner and Cristian Schoch). Tree and shrub species and varieties were introduced from Germany, France and Russia (Mauriņš & Zvirgzds, 2006). In 1878, Maximilian von Sivers established the Skrīveri Arboretum and introduced many exotic plant species to Latvia (Cinovskis et al., 1991; Mauriņš & Zvirgzds, 2006).

Dendrological plantations in Latvia were intensively studied in the 20th century. The dendroflora of urban and rural parks and dendrological plantations (in total 4,806 sites), including trees and shrubs was investigated between 1971–1990 by dendrologists of the Botanical Garden of the Latvian SSR Academy of Sciences under the leadership of Dr Raimonds Cinovskis (Cinovskis et al., 1974; Laiviņš et al., 2009). In the study of Laiviņš et al., (2009), the list of dendrological plantations included parks, old fragments of parks, miniparks, the largest old private collections in Latvia. However, plantings in cemeteries and private houses were not assessed in this study.

Over the last 200 years, the number of alien tree and shrub taxa in synanthropic habitats have significantly increased. Most were introduced as garden and park plants. Furthermore, plant species invasions begin in these greeneries. In the context of global warming trends, the number of such taxa escaping from greeneries will increase in the near future (Laiviņš et al., 2009). Currently, however, the rate of human-assisted migration (i.e., invasion sensu Pyšek et al. (2004)) of tree and shrub species is relatively faster than 150 years ago. Humans have been relocating plant species for centuries, but human-assisted plant migration is currently accelerating due to increased international trade (Rejmánek et al., 2013).

Currently, the largest dendrological plantations in Latvia are found in the National Botanic Garden (about 4,000 tree and shrub taxa) and the Kalsnava Arboretum (2,268 taxa; Evarts-Bunders et al., 2021). Considering that a total of 112 tree and shrub species are found in nature in Latvia, the number of species, subspecies, varieties, and hybrids, cultivated in these collections is huge. Many of these taxa are introduced from areas with a similar climate to Latvia – North America, Asia, and therefore, these taxa can easily move to the wild in Latvia.

Recently the global database of invasive trees and shrubs was updated, including a total of 751 species (434 trees and 317 shrubs) from 90 families (Rejmánek & Richardson, 2013; Rejmánek, 2014). The first list of alien organism species in Latvia was compiled in 2007 and includes 637 vascular plant taxa, of which 155 are trees and shrubs (Svilāns et al., 2007). However, due to global climate change that is facilitating the rapid expansion of alien species, several of which are also invasive, it is necessary to combine knowledge about the occurrence of all alien tree and shrub species in Latvia.

Successful invasion by alien species is almost irreversible, because most invasive alien plant species are successively established in large numbers before they are observed. Subsequently, they are almost impossible and very expensive to eliminate (Anonymous, 2019). Some of the most significant invasive plant species are cultivated trees and shrubs, which have been cultivated for a long time, successfully naturalized, and are now classified as invasive, ecologically aggressive ‘problematic’ plants. All seed-producing (and even some sterile) trees and shrubs have the ability to spread (Rejmánek et al., 1982; Huntley & Birks, 1983; MacDonald, 1993; Petit et al., 2004; Bialozyt et al., 2012; Rejmánek, 2014). Therefore, it is necessary to assess the current level of invasiveness of alien tree and shrub species, as well as the invasiveness risk level of these species in Latvia.

The aim of the study is to increase knowledge about alien tree and shrub species distribution in Latvia and to evaluate their invasiveness in relation to significant species traits. The objectives of the study are: 1) to update the list of alien tree and shrub species in Latvia; 2) to evaluate the invasiveness of alien trees and shrubs (degree of naturalization); 3) to assess the invasiveness risk in association with species origin and important traits: status and reproduction strategy. Our hypotheses are as follows: 1) species introduced to Latvia from distant regions (e.g., Asia, North America) will have a significantly higher invasiveness risk; 2) the risk of invasiveness and the status of the species are closely related to their reproduction strategy.

Material and Methods

Compiling data for an annotated list of invasive tree and shrub species

The list of invasive tree and shrub species was updated based on earlier research of woody flora in dendrological plantations in Latvia conducted from 1971 to 1990 under the guidance of the dendrologist Raimonds Cinovskis of the Botanic Garden of the Latvian Academy of Sciences (currently the National Botanic Garden), when a total of 4,806 dendrological plantations were inventoried. The lists of native and alien tree and shrub species were later published in the Atlas of Latvian Woody Plants (Laiviņš et al., 2009), with information about the number of locations and potential invasiveness. In this study, previous knowledge on the occurrence of taxa and comments on species invasiveness have been used and are presented in detail. The list of Latvian alien species from 2007 was also used in updating the list of invasive species (Svilāns et al., 2007). The updated annotated list of 178 alien taxa with traits of invasiveness in Latvia has been compiled in Appendix 1. In order to update the list of invasive tree and shrub species, a total of 145 dendrological plantations and parks in the territory of Latvia in the period from 2006 to 2020 were inventoried (Figure 1). During the dendrological inventory, the presence of invasive tree and shrub species in the park and its vicinity was assessed – within a radius of approximately 50 m around park boundaries. Active vegetative and generative reproduction was assessed, also assessing whether the species grows in sites where it has not been planted previously. Some dendrological plantations have been inspected twice in this period – if it was not possible to collect qualitative data (e.g., due to mowing, or an inappropriate season) – Alūksne Park, Aizvīķu Parks, Eleja Park, Hoftenberga Park, Ilga Park, Juzefova Park, Kalsnava Arboretum, Kazdanga Park, Krāslava Park, Krote Park, Lielauce Park, Lielezere Park, National Botanic Garden, Preiļi Park, Skrīveri Arboretum, Talsi Dendrological Park, Vabole Park, Vecsaule Park, Vilce Park, Višķi Park, Zentene Park.

Figure 1

The locations of the studied dendrological plantations in Latvia.

In order to provide as detailed information as possible on the 178 listed tree and shrub taxa, the following information is provided in Appendix 1:

  1. Taxonomic affiliation of the listed trees and shrubs to genera.

  2. First report in the area. This column provides a summary of when the non-native woody plant species were introduced into the territory of Latvia, based on the first publication date (Laiviņš et al., 2009).

  3. Origin.

  4. Non-native tree and shrub species were classified as alien, casual alien, naturalized, invasive and transformers or weeds following Pyšek et al. (2004) accordingly: Casual alien plants: alien plants that under favourable conditions can occasionally reproduce in the wild but are unable to form sustainable populations. These fail to exist in the area for an extended period without re-introduction. Naturalized alien plants: alien plants that sustain self-replacing populations for more than 10 years, supplemented by offspring that are able to grow independently. Invasive plants: plants which are naturalized, that produce fertile offspring, commonly in very large numbers, and thus are able to spread over a large area. Transformers: invasive plants that degrade ecosystems in a substantial area. Dual status: species, which occur naturally in some parts of Latvia, but, at the same time, have been cultivated and spread in the wild.

  5. Vector. The mode of entry into Latvia is indicated for each taxon. The status describes the types of introduction of alien species as classified according to Stace & Crawley (2015). The evaluated trees and shrubs have two types of introduction in Latvia: F – as edible (human food), including herbs and spices, plant seeds, fruits and other plant parts; H – horticultural introductions.

  6. The type of spreading indicates whether the species reproduces in Latvia from seed and/or by vegetative propagation. The data were summarized based on the authors’ observations and literature.

  7. Species distribution in Latvia was estimated by applying the square method, which is related to the geographical coordinates, where one square corresponds approximately to 7.6 × 9.3 km or 71 km2 for Latvia. The total number of the grid cells in Latvia is 1,017, from which 822 are completely and 195 partially located in the territory of Latvia (Laiviņš et al., 2009).

  8. Invasiveness risk. There are many challenges facing the field of risk assessment of species invasiveness. After revision of previously used methods (e.g., Pheloung, 1995; Van Wilgen et al., 2001; Andersen et al., 2004; Genovesi & Shine, 2004; Burgiel & Muir, 2010; Verbrugge et al., 2010; Crossman et al., 2011; McDougall et al., 2011; Sandvik et al., 2013) we have decided to follow the methodology of Weber & Gut (2004), where fairly simple criteria were used for assessing the potential risk of invasive woody plant species. The rating system allocates scores to the species for biogeographical, ecological, and experience-linked aspects. In this work the authors used 12 questions for the assessment, for which points have been awarded. We adapted the selected scheme to Latvian conditions and made corresponding changes. The term “Europe” has been changed to “Northern Europe”. It was important to change this criterion, as a number of species found in nature in Central Europe have been introduced in Latvia and exhibit features of invasiveness.

  9. Risk class. Each non-native woody plant species was assigned to one of the three risk classes, based on the total point score as follows (Weber & Gut, 2004): 3–20 low risk – species is unlikely to pose a threat to natural communities; 21–27 intermediate risk – species requires further observation; 28–38 high risk – species is likely to become a threat to natural communities if naturalized.

Data analysis

We applied Pearson’s Chi-squared test for count data corresponding to the number of species (Hope, 1968) to evaluate the dependence between species invasiveness risk class and the following species characteristics: native distribution range (Europe, North America, Asia/Eastern Asia, Eurasia, Europe/Asia Minor, Eurosiberia, cultivar) for 178 species, status (transformer, invasive, casual, dual, natural) for 178 species and reproduction strategy (seeds, vegetative, seeds and vegetative) for 171 species.

To identify the most contributing associations of the Pearson’s Chi-squared test results among species invasiveness risk class and native distribution range and among invasiveness risk class and status, Pearson’s residuals were calculated from the Pearson’s Chi-squared test results and visualized using the ‘corrplot’ package (Wei & Simko, 2017). All data analyses were conducted in R (R Core Team, 2020).

Results

Updated list of invasive trees and shrubs

The new annotated list of invasive trees and shrubs includes 178 taxa. The previous list of alien species (Svilāns et al., 2007) has been supplemented with 46 new tree and shrub taxa (Appendix 1). Three species have naturalized – Salix daphnoides Vill., S. × fragilis L., Syringa villosa Vahl; six taxa are invasive – Aronia × prunifolia ‘Floribunda’, Populus longifolia Fisch., P. ‘Lettland’, Rosa × malyi A. Kern., R. × regeliana Linden & Andr, Spiraea × rosalba Dippel; one species has dual status – Salix acutifolia Willd. We identified eleven most widespread casual alien tree and shrub species – Acer tataricum L. subsp. ginnala (Maxim.) Wesm., Celastrus orbiculatus Thunb., Forsythia × intermedia Zabel, Juglans mandshurica Maxim., Juniperus sabina L., Malus sieboldii (Regel) Rehder, Padus maackii (Rupr.) Kom., Philadelphus coronarius L., Pinus strobus L., Spiraea japonica L., Syringa josikaea Jacq. Fil. ex Rchb.

In total, 23 taxa from the previous alien plant list are not included in the current updated list. We did not find confirmation of the migration of these 23 alien taxa into the wild in the areas inspected during the study, for example, Crataegus × media Bechst., C. × uhrovae Soó, Genista pilosa L., Malus dasyphylla Borkh., Rosa acicularis Lindl., R. multiflora Thunb., and R. alba L.

Number and composition of taxa

The list of alien tree and shrub species in Latvia includes representatives from 28 families. There are five families with at least 10 species classified as alien that together comprise 62.36% of the total alien taxa of the country. The most frequent are from the Rosaceae family, containing 51 taxa (corresponding to 28.65% of all alien tree and shrub species), the Salicaceae family with 20 taxa (11.24%), the Aceraceae family with 15 taxa (8.43%), the Fabaceae family with 13 taxa, (7.30%), and the Pinaceae family with 12 taxa, (6.74%) (Appendix 1).

Of the taxa analysed, conifers are represented by 14 taxa (7.86%), belonging to two families Cupressaceae – 2 taxa (1.12%) and Pinaceae – 12 taxa (6.74%). The remaining 92.14% of species belong to deciduous trees. Acer – 15% of taxa, Spiraea – 11%, Populus – 10% and Salix – 10%. These are the most represented genera in the updated list of invasive alien species.

Plant traits

Most of the 178 alien taxa introduced in Latvia are native to North America (46 taxa, 26%), and Europe (39 taxa, 22%), the rest originated from Eurasia (17 taxa, 10%), East Asia (20 taxa, 11%) or are cultivars – decorative varieties, hybrids and other taxa without a natural native area (32 taxa, 18%; Figure 2, Appendix 1). In total, 18% of the studied alien taxa are cultivars.

Figure 2

Share of the assessed species by origin.

During this study, 178 tree and shrub taxa were evaluated according to the selected criteria. In Latvia, all these species are successful at self-reproducing, of which two species (1%) are recognized as transformers: Acer negundo L. and Sorbaria sorbifolia (L.) A. Braun. Altogether, 42 species are considered invasive (24%), 23 – naturalized (13%); dual status was assigned to nine species (5%) and 104 species (57%) have casual status (Figure 3). After evaluating all alien tree and shrub species, which showed possible invasiveness, 44 taxa (25%) have been classified as aggressive invasive species in Latvia.

Figure 3

Distribution of alien trees and shrubs by invasiveness status.

The results show that 89% of the identified invasive plants dispersed from horticulture, 6% as edible plants, including herbs and plant seeds, fruits and other plant parts, 3% horticulture and human food and 2% horticulture and timber.

Risk assessment

This study provides a risk assessment of invasive plants for all 178 tree and shrub taxa that show signs of invasiveness after introduction in Latvia. According to the scores obtained through the risk assessment, the taxa are divided into three risk classes. Class III (high risk) includes 32 species (18%). The alien taxa to belong to the high-risk class are: Acer negundo L., A. pseudoplatanus L., A. tataricum L. subsp. ginnala (Maxim.) Wesm., Amelanchier spicata (Lam.) K. Koch, Celastrus orbiculatus Thunb., Cotoneaster lucidus Schlecht., Elaeagnus argentea Pursh., Hippophaë rhamnoides L., Parthenocissus quinquefolia (L.) Planch., Populus laurifolia Ledeb., P. longifolia Fisch., Rosa rugosa Thunb., Salix alba L., Spiraea × billardii Herincq., S. × rosalba Dippel.

Class II (intermediate risk) includes 123 taxa or 69% of the alien species, while class I (low risk) includes 23 taxa or 13% of all alien taxa (Appendix 1). All three risk classes were present in each of the five alien species status categories (Figure 4). Class III included 23 species from the invasive taxa group (Appendix 1), the transformer Acer negundo and four species from the casual taxa group – Acer tataricum subsp. ginnala, Celastrus orbiculatus, Cerasus tomentosa (Thunb.) Wall., Salix alba ‘Vitellina’. Class III also included taxa with dual status (Salix alba) and three taxa from the naturalized taxa group (Salix alba ‘Sericea’, Salix daphnoides, Salix × fragilis) (Figure 4).

Figure 4

Number of studied tree and shrub taxa among invasiveness statuses and risk classes.

We did not find significant differences between the area of origin of the taxa and invasiveness risk classes (X2=16.26, p=0.28). Of the 32 taxa in Class III (high-risk class), 10 taxa or 31.25% are cultivated, 8 taxa or 25% are of North American origin, and four are from East Asia. Eurosiberian taxa were not found in Class III (Figure 5, Appendix 1).

Figure 5

Number of studied tree and shrub taxa among origins and risk classes.

Associations between invasiveness risk classes and plant traits of trees and shrubs with different origin

We did not find a significant association between the studied species invasiveness risk class and species native distribution range (X2=16.26, p=0.30). A significant association was found between the species invasiveness risk class and species status (X2=55.92, p<0.01) and between the invasiveness risk class and species reproduction strategy (X2=61.25, p<0.01).

Pearson’s residuals showed the association between all three invasiveness risk classes and invasive and casual species status (Figure 6 A) which contributed to Pearson’s Chi-squared test results. The highest positive association was found between a high invasiveness risk class and invasive species status, but the highest negative association was found between a high invasiveness risk class and casual species status (Figure 6 A).

Figure 6

Contributing associations between species invasiveness risk classes (High, Intermediate, Low) and species statuses (Transformer, Invasive, Casual, Dual, Natural) (A) and species invasiveness risk classes and species reproduction strategies (Seeds, Vegetative, Seeds/Vegetative) (B) based on Pearson’s residuals obtained from the Chi-squared test results. The colour map refers to Pearson’s residual values and the circle size refers to the magnitude of positive or negative associations.

Pearson’s residuals showed the association between all three invasiveness risk classes and all three reproduction strategies (Figure 6 B) which contributed to the Pearson’s Chi-squared test results. The highest contribution was found between a high invasiveness risk class and species having both seed and vegetative reproduction strategies, which showed a positive association. A high contribution was also found in the positive association between vegetative reproduction and low invasiveness risk. A high contribution was also found in the negative association between a high invasiveness risk class and species reproducing by seeds (Figure 6 B).

Discussion

As a result of this study, a national list of alien tree and shrub species was compiled, assessing observed invasiveness traits for the included species. The aim of a risk assessment for invasive trees and shrubs was to estimate which species should be listed on the national invasive plant list and to decide which new species infestations should be controlled or removed in order to prevent their spread and associated ecological consequences (Weber & Gut, 2004).

We did not prove the hypothesis that species from distant locations like Asia and North America show more pronounced invasiveness traits, namely, a higher risk class of invasiveness (Figure 5). This can be explained by the number of cultivars in our dataset. Accordingly, in other similar research (Andreu & Vilá, 2010; Fayvush et al., 2018; Nutt & Kubjas, 2020), no associations were established between species origin and invasiveness classes.

In the present study, of the 32 tree and shrub taxa included in the high-risk invasiveness class, a considerable number of them were cultivars or hybrids of horticultural origin – 10 (31.25%), and an addition eight (25%), originated from North America. The majority of cultivars with a high risk of invasiveness belong to Rosaceae: Cerasus vulgaris, Rosa × malyi, R. pimpinellifolia L., R. × regeliana, Spiraea × billardii, S. × rosalba. The following cultivars are also in the high-risk invasiveness group: Salix alba ‘Sericea’, Salix alba ‘Vitellina’ and Acer pseudoplatanus ‘Purpurascens’.

The family Rosaceae is the most widely represented in the list of invasive tree and shrub taxa (51 taxa, corresponding to 28.65% of all trees and shrubs aliens). Asia is the major source of invasive Rosaceae shrubs, as well as invasive Oleaceae species. Most of the invasive Salicaceae are of Eurasian origin. Because of increasing connections with many Asian countries, even more invasive tree and shrub species will be introduced from Asia (Rejmánek, 2014). The number of tree and shrub species with Asian origin has increased in Latvian nurseries in recent years, for example, Ailanthus altissima (Mill.) Swingle, Lespedeza bicolor Turcz., Morus alba L., Paulownia tomentosa (Thunb.) Steud. and Wisteria floribunda (Willd.) DC. (Anonymous, 2021). With increasing trade, we can expect that more alien tree and shrub taxa will sooner or later become invasive in the Baltic region. At present, in the first half of the 21st century, Ailanthus altissima, Paulownia tomentosa and Wisteria floribunda suffer from frost damage in Latvia, but in suitable climatic conditions they can survive.

The second hypothesis stated that the risk of invasiveness and the status of the species is closely related to the reproduction strategy. We have shown that species that reproduce both vegetatively and by seed dispersion are more aggressive and invade larger areas more quickly in comparison to other alien species (Stace & Crawley, 2015). For example, Acer negundo, Elaeagnus argentea, Hippophaë rhamnoides, Parthenocissus quinquefolia, Physocarpus opulifolius. (L.) Maxim. Such species may be used for berry production in plantations only under strict control. For aggressive invasive alien species, varieties with variegated leaves with slowed photosynthesis are recommended for landscape gardening (Gaskin & Kazmer, 2009), so that the taxon grows slowly and is less aggressive. Interspecific hybrids that do not produce germinating seeds are also recommended for landscape gardening as self-seeding is not possible for such taxa (Gaskin & Kazmer, 2009).

When creating parks, squares, and backyard greeneries, we recommend avoiding taxa included in the high invasiveness risk class in order to prevent the invasion of large areas by adult trees and shrubs that are already capable of producing seeds. In old parks where they were planted, taxa such as Spiraea, Swida and Syringa, are currently migrating to natural areas. Invasive species in natural habitats need to be controlled so that they do not destroy natural ecosystems.

Conclusions

Our study resulted in the compilation of an updated list of 178 alien tree and shrub taxa, that were identified as migrating into natural ecosystems (self-seeding). A total of 44 tree and shrub taxa have been identified as aggressive invasive species, either potentially invasive (with transformer status) or invasive.

Three classes of invasiveness risks were distinguished. The majority of alien tree and shrub species are already invasive – 18% of evaluated species belong to the high-risk class of invasiveness, or have a great potential to become invasive in future – 69% of species belong to the intermediate invasiveness risk group, and only few alien taxa (12% of species) have a low risk of invasiveness. High-risk class species should be given special attention and monitoring in order to prevent the invasion of large areas by these species in the future. In addition, species with intermediate risk of invasiveness also require monitoring and periodic assessment as these taxa may become potentially hazardous over time.

Invasiveness risk and species status are closely related to reproduction strategy. We have proved that species that are able to reproduce both vegetatively and by seed dispersion are more aggressive and invade larger areas more quickly than species with only vegetative reproduction (have low risk of invasiveness). The planting of invasive species with both reproduction strategies should therefore be avoided. Therefore, we recommend planting varieties and hybrids that do not produce germinating seeds, thus avoiding self-seeding.

The Weber and Gut method is suitable for risk assessment of alien tree and shrub taxa in Latvia. Subsequently, the assessment of the tree and shrub taxa yielded interesting and reliable results, which can be used to assess the potential invasiveness risk of a species. The updated tree and shrub species list can be included in the list of invasive species of Latvia. The results of the present study can be used in future studies about alien tree and shrub species’ distributional changes due to the global climate change. The results also contribute to practical nature conservation and landscape gardening in regions with similar climatic conditions.

Acknowledgements

Part of the work was supported by Daugavpils University project “Taxonomical and chorological studies on rare and autochthonous species of genus Rosa L. in Latvia.” (Nr. 14-95/2022/4). The study was partly financially supported by the Fundamental and Applied Science project of Latvian Council of Science: No. lzp-2020/1-0314 “Bryophyte and lichen successional and spatial patterns in deciduous forests”. Thanks to Inita Svilāne (Daugavpils University, Latvia) for creating the cartographic material. We are grateful to Dainis Edgars Ruņģis for consultation in English language and the reviewers for valuable comments that helped to improve the article.

Appendices

Appendix 1

Updated list of invasive tree and shrub taxa with traits of invasiveness in Latvia.

Abbreviations: Vector: F – edible plants, including herbs and spices, and fruit seeds or fruits; H – horticultural introductions, mainly ornamentals, but also grassland, hedging, game cover and green manure; T – with timber (Stace & Crawley, 2015); Type of spreading – indicates whether the species reproduces in Latvia from seed (s) and/or from vegetative propagation (v); Species distribution in Latvia – according to our data and literature (Laiviņš et al., 2009); - no data.

NoSpeciesFamilyFirst reported in the areaOriginStatus of alien taxaVectorType of spreadingSpecies distribution in Latvia (grid cells)Invasiveness riskRisk class
1.Abies alba Mill.Pinaceae1817EuropecasualHs15022II
2.Abies balsamea (L.) Mill.Pinaceae1805N AmericacasualHs17224II
3.Abies concolor (Gordon & Glend.) Lindl. ex Hildebr.Pinaceae1888N AmericacasualHs14724II
4.Abies nordmanniana (Stev.) SpachPinaceae1867EuropecasualHs2224II
5.Abies sibirica Ledeb.Pinaceae1856AsiacasualHs36221II
6.Abies × phanerolepis FernaldPinaceae-N AmericacasualHs20423II
7.Acer barbinerve Maxim.Aceraceae1957East AsiacasualHs822II
8.Acer campestre L.Aceraceae1805Europe, Asia MinorcasualHs7326II
9.Acer circinatum PurshAceraceae1963N AmericacasualHs822II
10.Acer mono Maxim. var. mayrii (Schwer.) NakaiAceraceae1969East AsiacasualHs522II
11.Acer negundo L.Aceraceae1817N AmericatransformerHs/v49834III
12.Acer palmatum Thunb. subsp. amoenum (Carriėre) HaraAceraceae1958EurasiacasualHs121II
13.Acer platanoides ‘Crimson King’Aceraceae-CultivarcasualHs1724II
14.Acer platanoides ‘Schwedleri’Aceraceae1883CultivarcasualHs4426II
15.Acer pseudoplatanus L.Aceraceae1804EurasiainvasiveHs21031III
16.Acer pseudoplatanus ‘Purpurascens’Aceraceae1805CultivarinvasiveHs1729III
17.Acer pseudosieboldianum (Pax) Kom.Aceraceae-East AsiacasualHs1024II
18.Acer saccharinum L.Aceraceae1805N AmericacasualHs11925II
19.Acer tataricum L. subsp. ginnala (Maxim.) Wesm.Aceraceae1876EurasiacasualHs28029III
20.Acer tataricum L. subsp. tataricumAceraceae1805EurasiacasualHs17827II
21.Acer tegmentosum Maxim.Aceraceae1880EurasiacasualHs922II
22.Aesculus hippocastanum L.Hippocastanaceae1805Europe, Asia MinorcasualHs99620I
23.Amelanchier spicata (Lam.) K. KochRosaceae1888N AmericainvasiveHs123531III
24.Aralia elata (Miq.) Seem.Araliaacee1877East AsiacasualHv3820I
25.Aronia × prunifolia ‘Floribunda’Rosaceae1902CultivarinvasiveHs/v37127II
26.Artemisia abrotanum L.Asteraceae-EuropecasualH-17821II
27.Berberis thunbergii DCBerberidaceae1880East AsiacasualHs32426II
28.Berberis vulgaris ‘Atropurpurea’Berberidaceae-CultivarcasualHs-26II
29.Caragana arborescens Lam.Fabaceae1805East AsiainvasiveHs/v125628III
30.Caragana frutex (L.) K. KochFabaceae1817EurosibiriainvasiveHs/v26926II
31.Carpinus betulus L.Corylaceae-Europedual statusHs19021II
32.Celastrus orbiculatus Thunb.Celastraceae1873East AsiacasualHs/v6029III
33.Cerasus avium (L.) MoenchRosaceae1778Europe, Asia MinorinvasiveFs/v31425II
34.Cerasus tomentosa (Thunb.) Wall.Rosaceae1930East AsiacasualFs/v4329III
35.Cerasus vulgaris Mill.Rosaceae-CultivarinvasiveFs/v-29III
36.Chaenomeles japonica (Thunb.) Lind. ex SpachRosaceae1867East AsiacasualF,Hs36525II
37.Chamaecytisus ratisbonensis (Schaeff.) Rothm.Fabaceae1888Europe, SiberiacasualHs/v2125II
38.Clematis recta L.Ranunculaceae1976EuropecasualHs/v1227II
39.Cotoneaster dammerii C. K. Schneid.Rosaceae1960East AsiacasualHs2624II
40.Cotoneaster lucidus Schlecht.Rosaceae1884AsiainvasiveHs61229III
41.Cotoneaster multiflorus BungeRosaceae1888AsiacasualHs1822II
42.Crataegus alemanniensis CinovskisRosaceae1971EuropenaturalizedHs35825II
43.Crataegus douglasii Lindl.Rosaceae1867N AmericacasualHs6424II
44.Crataegus flabellata (Bosc) K. KochRosaceae1965N AmericacasualHs7124II
45.Crataegus laevigata (Poir.) DCRosaceae-Europedual statusHs-25II
46.Crataegus monogyna Jacq.Rosaceae1859EuropecasualHs2325II
47.Crataegus submollis Sarg.Rosaceae1856N AmericacasualHs21624II
48.Cytisus scoparius (L.) LinkFabaceae1892EuropeinvasiveHs4222II
49.Elaeagnus angustifolia L.Elaeagnaceae1817EurasiacasualHs/v1522II
50.Elaeagnus argentea Pursh.Elaeagnaceae1877N AmericainvasiveHs/v18731III
51.Euonymus nanus M. Bieb.Celastraceae1867EurasiacasualHs/v3225II
52.Fagus sylvatica L.Fagaceae1805EuropeinvasiveHs26323II
53.Fagus sylvatica ‘Purpurea Latifolia’Fagaceae-CultivarinvasiveHs-24II
54.Forsythia suspensa (Thunb.) VahlOleaceae1880East AsiacasualHv6424II
55.Forsythia × intermedia ZabelOleaceae1894CultivarcasualHv12324II
56.Fraxinus pennsylvanica MarchallOleaceae1821N AmericacasualHs11724II
57.Fraxinus pennsylvanica Marchall var. subinetegerrima (Vahl) Fern.Oleaceae1856N AmericacasualHs11724II
58.Genista tinctoria L.Fabaceae1805EurosibiriacasualHs2320I
59.Grossularia reclinata (L.) Mill. var. reclinataGrossulariaceae-EuropenaturalizedFs48127II
60.Grossularia reclinata (L.) Mill. var. uva-crispa (L.) BergerGrossulariaceae-EuropenaturalizedFs-24II
61.Hedera helix L. var. helixAraliaceae1817EuropecasualHv4118I
62.Hedera hibernica (Kirchn.) BeanAraliaceae1867EuropecasualHv918I
63.Hippophaë rhamnoides L.Elaeagnaceae1817EurasiainvasiveF,Hs/v23028III
64.Hydrangea paniculata ‘Grandiflora’Hydrangeaceae1884CultivarcasualHs4924II
65.Hyssopus officinalis L.Labiatae-EuropecasualFs-19I
66.Juglans ailanthifolia CarriėreJuglandaceae1884East AsiacasualHs5227II
67.Juglans cinerea L.Juglandaceae1847N AmericacasualHs24227II
68.Juglans mandshurica Maxim.Juglandaceae1910East AsiacasualHs11927II
69.Juniperus sabina L.Cupressaceae1819EurasiacasualHs14324II
70.Larix decidua Mill.Pinaceae1805EuropenaturalizedHs76325II
71.Lavandula angustifolia Mill.Labiatae-EuropecasualF,Hs716I
72.Ligustrum vulgare L.Oleaceae1805Europe, Asia MinornaturalizedHs37822II
73.Lonicera caerulea L.Caprifoliaceae1805EurasiacasualHs2622II
74.Lonicera caprifolium L.Caprifoliaceae1805EuropecasualHs/v37724II
75.Lonicera periclymenum L.Caprifoliaceae1805EuropecasualHs/v11224II
76.Lonicera tatarica L.Caprifoliaceae1805EurasianaturalizedHs57327II
77.Lycium barbarum L.Solanaceae1805EurasiacasualHs/v2721II
78.Mahonia aquifolium L.Berberidaceae1853N AmericacasualHs17824II
79.Malus baccata (L.) Borkh.Rosaceae1805East AsiacasualHs3327II
80.Malus domestica Borkh.Rosaceae1778CultivarinvasiveFs11727II
81.Malus pumila Mill.Rosaceae1805CultivarcasualHs422II
82.Malus × purpurea (Barbier) RehderRosaceae1956CultivarcasualHs2924II
83.Malus sachalinensis Juz.Rosaceae1959East AsiacasualHs724II
84.Malus sieboldii (Regel) RehderRosaceae1885East AsiacasualHs2024II
85.Malus sieversii (Ledeb.) M. Roem.Rosaceae1888AsiacasualHs2724II
86.Oxycoccus macrocarpus (Aiton) Pursh.Ericaceae-N AmericacasualFs-27II
87.Padus maackii (Rupr.) Kom.Rosaceae1956N AmericacasualHs2823II
88.Padus serotina (Ehrh.) Borkh.Rosaceae1805N AmericacasualHs3823II
89.Parthenocissus inserta (A. Kern.) FritschVitaceae1929N AmericacasualHs/v2426II
90.Parthenocissus quinquefolia (L.) Planch.Vitaceae1847N AmericainvasiveHs/v21031III
91.Pentaphylloides fruticosa (L.) O. SchwarzRosaceae-Cultivardual statusHs8624II
92.Philadelphus coronarius L.Hydrangeaceae1805EuropecasualHs122921II
93.Philadelphus pubescens Loisel. var. verrucosus (Schrad.) S.Y.HuHydrangeaceae1856N AmericacasualHs47423II
94.Physocarpus opulifolius (L.) Maxim.Rosaceae1805N AmericainvasiveHs/v36629III
95.Picea glauca (Moench) VossPinaceae1805N AmericacasualHs19424II
96.Pinus mugo TurraPinaceae1805EuropecasualHs10322II
97.Pinus strobus L.Pinaceae1805N AmericacasualH,Ts16627II
98.Populus alba L.Salicaceae1805EurasiainvasiveHs/v45127II
99.Populus alba ‘Nivea’Salicaceae-CultivarcasualHv-26II
100.Populus balsamifera L.Salicaceae1805N AmericanaturalizedHs/v61826II
101.Populus × berolinensis K. KochSalicaceae1879EuropecasualH-11820I
102.Populus × canadensis MoenchSalicaceae-CultivarnaturalizedHv25120I
103.Populus × canescens (Aiton) Sm.Salicaceae-Europe, Asia MinornaturalizedHv17320I
104.Populus ‘Lettland’Salicaceae-CultivarinvasiveHv34920I
105.Populus laurifolia Ledeb.Salicaceae1856AsiainvasiveH,Ts/v6929III
106.Populus longifolia Fisch.Salicaceae1847N AmericainvasiveHs/v29829III
107.Populus trichocarpa Torr. & A. GraySalicaceae1913N AmericacasualH,Tv3320I
108.Prunus cerasifera Ehrh. var. divaricata (Ledeb.) BaileyRosaceae1883Europe, Asia MinorinvasiveF,Hs/v36629III
109.Prunus domestica L. var. instititia (L.) C.K. Schneid.Rosaceae1888EuropeinvasiveF,Hs/v1529III
110.Prunus spinosa L.Rosaceae-Europedual statusHs/v-27II
111.Pseudotsuga menziesii (Mirb.) Franco var. menziesiiPinaceae1888N AmericacasualHs15324II
112.Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) FrancoPinaceae1883N AmericacasualHs16224II
113.Pterocarya fraxinifolia (Poir.) SpachJuglandaceae1867AsiacasualHv1420I
114.Pyrus communis L.Rosaceae-EuropecasualFs-25II
115.Quercus petraea (Matt.) Liebl.Fagaceae1968EuropecasualHs1318I
116.Quercus rubra L.Fagaceae1859N AmericainvasiveH,Ts18327II
117.Rododendron catawbiense Michx.Ericaceae1872N AmericacasualHs3224II
118.Rododendron japonicum (A.Gray) J.V. SuringarEricaceae1877East AsiacasualHs5024II
119.Rhus typhina L.Anacardiaceae1817N AmericacasualHv15220I
120.Ribes nigrum L.Grossulariaceae-Eurasiadual statusFv/s164626II
121.Ribes rubrum L.Grossulariaceae-EuropenaturalizedFs140827II
122.Robinia luxurians (Diec ex Goehabitatze) C.K. Schneid.Fabaceae1909N AmericainvasiveHs6722II
123.Robinia pseudoacacia L.Fabaceae1805N AmericainvasiveHs32325II
124.Robinia pseudoacacia ‘Semperflorens’Fabaceae-CultivarinvasiveHs-22II
125.Robinia viscosa var. hartwigii (Koehne) AsheFabaceae1961N AmericainvasiveHs4522II
126.Rosa glabrifolia C.A. Mey. ex Rupr.Rosaceae1894Europe, SiberianaturalizedHs17224II
127.Rosa glauca Pourr.Rosaceae1888EuropenaturalizedHs19527II
128.Rosa × malyi A. Kern.Rosaceae-CultivarinvasiveHs/v-29III
129.Rosa pimpinellifolia L.Rosaceae1805CultivarinvasiveHs/v114029III
130.R. pomifera Herrm. subsp. pomiferaRosaceae1894Europe, Asia MinorcasualHs15626II
131.Rosa × regeliana Linden & AndrRosaceae-CultivarinvasiveHs/v-31III
132.Rosa rugosa Thunb.Rosaceae1888East AsiainvasiveHs/v87233III
133.Rubus odoratus L.Rosaceae1805N AmericanaturalizedHs/v6424II
134.Rubus parviflorus Nutt.Rosaceae1859N AmericacasualHs/v1524II
135.Salix acutifolia Willd.Salicaceae-Europedual statusHs/v51027II
136.Salix acutifolia × S. daphnoidesSalicaceae-Cultivardual statusHs/v16727II
137.Salix alba L.Salicaceae-Europedual statusHs/v134929III
138.Salix alba ‘Britzensis’Salicaceae-CultivarcasualHs/v-26II
139.Salix alba ‘Sericea’Salicaceae1875CultivarnaturalizedHs/v41729III
140.Salix alba ‘Vitellina’Salicaceae1805CultivarcasualHs/v12929III
141.Salix daphnoides Vill.Salicaceae1839EuropenaturalizedHs/v27129III
142.Salix euxina I.V. BelyaevaSalicaceae1791EuropenaturalizedHs/v197427II
143.Salix purpurea ‘Lambertiana’Salicaceae-CultivarcasualHs/v-26II
144.Salix × fragilis L.Salicaceae1853CultivarnaturalizedHs/v9228III
145.Sambucus nigra L.Caprifoliaceae1805Europe, Asia MinorinvasiveHs48723II
146.Sambucus racemosa L.Caprifoliaceae1805EurasiainvasiveHs104827II
147.Sambucus racemosa ‘Plumosa’Caprifoliaceae-CultivarcasualHs-24II
148.Sorbaria sorbifolia (L.) A. BraunRosaceae1805AsiatransformerHs/v70527II
149.Spiraea alba Du RoiRosaceae1885N AmericainvasiveHs/v71728III
150.Spiraea betulifolia Pall.Rosaceae1960East AsiacasualHs1821II
151.Spiraea × billardii Herincq.Rosaceae1856CultivarinvasiveHv28328III
152.Spiraea chamaedryfolia L.Rosaceae1805AsiainvasiveHs70222II
153.Spiraea douglasii Hook.Rosaceae1847N AmericacasualHs/v1223II
154.Spiraea japonica L.Rosaceae1859CultivarcasualH-11322II
155.Spiraea latifolia (Aiton) Borkh.Rosaceae1817N AmericacasualH-4720I
156.Spiraea media F. SchmidtRosaceae1856EurasianaturalizedH-40521II
157.Spiraea menziesii Hook.Rosaceae1913N AmericacasualH-520I
158.Spiraea nipponica Maxim.Rosaceae1964East AsiacasualH-1418I
159.Spiraea × rosalba DippelRosaceae-CultivarinvasiveHv4729III
160.Swida alba (L.) OpizCornaceae1805AsiainvasiveHv44129III
161.Swida alba ‘Sibirica’Cornaceae-CultivarcasualHv-25II
162.Swida sericea L.Cornaceae1817N AmericacasualHv2526II
163.Swida sericea ‘Flaviramea’Cornaceae-CultivarcasualHv-25II
164.Symphoricarpos albus (L.) S. F. Blake var. laevigatus (Fernald) S. F. BlakeCaprifoliaceae1805N AmericainvasiveHs/v93233III
165.Syringa josikaea Jacq. Fil. ex Rchb.Oleaceae1847EuropecasualHs34917I
166.Syringa villosa VahlOleaceae1955AsianaturalizedHs37619I
167.Syringa vulgaris L.Oleaceae1805EuropeinvasiveHv156526II
168.Teucrium chamaedrys L.Labiatae-Europedual statusHs-19I
169.Thuja occidentalis L.Cupressaceae1805N AmericacasualHs104725II
170.Thymus marschallianus Willd.Labiatae1932EurasiacasualHs917I
171.Tilia platyphyllos Scop. subsp. cordifoliaTiliaceae1805EuropenaturalizedHs19025II
172.Toxicodendron pubescens Mill.Anacardiaceae-N AmericacasualHv-23II
173.Ulmus minor Mill.Ulmaceae1877EuropenaturalizedHs8822II
174.Ulmus minor Mill. f. suberosa (Moench) Cin.Ulmaceae-EuropecasualHs1822II
175.Ulmus pumila L.Ulmaceae1956N AmericanaturalizedHs1524II
176.Viburnum lantana L.Caprifoliaceae1805EuropenaturalizedHs15725II
177.Vinca major L.Apocynaceae1856Europe, Asia MinorcasualHv419I
178.Vinca minor L.Apocynaceae1856Europe, Asia MinorinvasiveHv13626II
DOI: https://doi.org/10.2478/fsmu-2022-0001 | Journal eISSN: 1736-8723 | Journal ISSN: 1406-9954
Language: English, Estonian
Page range: 1 - 20
Submitted on: Jan 12, 2022
Accepted on: Feb 2, 2022
Published on: Feb 20, 2023
Published by: Estonian University of Life Sciences
In partnership with: Paradigm Publishing Services
Related subjects:

© 2023 Gunta Evarte-Bundere, Pēteris Evarts-Bunders, Anna Mežaka, Aiva Bojāre, published by Estonian University of Life Sciences
This work is licensed under the Creative Commons Attribution 4.0 License.