Invasive species are the second most important cause of extinction of plant and animal species, after habitat modification. The successful solution to this problem is the early detection of invasive species, as such action is easier and more effective.
Invasive non-native plants are plants that have been brought into an environment (either intentionally or unintentionally)
in which they did not evolve and thus usually have no natural enemies to limit their reproduction and spread. Their fast growth
characteristics, mechanisms for surviving unfavorable conditions and high reproductive rates allow them to "invade" the new habitats.
The primary legislation for managing invasive species in Slovenia is the Nature Conservation Act
(Official Gazette of the Republic of Slovenia, No. 96/04 – officially consolidated text, 61/06 – ZDru-1, 8/10 –
ZSKZ-B, 46/14, 21/18 – ZNOrg, 31/18, 82/20, 3/22 – ZDeb, 105/22 – ZZNŠPP and 18/23 – ZDU-1O).
European Regulation No. 1143/2014 on implementation of EU regulations on the prevention and management of
the introduction and spread of invasive alien species which has been in force since January 2015, defines the
invasive non-native species as follows: "invasive non-native species" means a non-native species whose introduction
or spread has been found to threaten or adversely impact upon biodiversity and related ecosystem services;
The regulation also specifies the measures that EU member states must take to prevent or limit damage caused
by invasive non-native species.
Invasive non-native species reproduce extremely quickly and can outcompete almost any other plant.
They destroy natural environments, displace native species, and interbreed with them, changing their genetic material,
changing ecosystem processes, and also supporting other non-native plants and animals. Some also cause health problems,
which can be highly allergenic, cause hay fever and skin damage. The biggest problems are caused by plants that change
essential processes in the ecosystem, such as the frequency of fires, the availability of water, mineral nutrients, and
affect soil erosion.
The removal and prevention of the spread of invasive non-native species is essential, primarily to reduce the damage they cause to the environment,
and at the same time it is necessary to comply with the European Regulation no. 1143/2014 on the prevention and control of the introduction and spread of
invasive non-native species. In protected areas, the management of non-native species is essential, where the main goal is the conservation of biodiversity.
Eradication of invasive plants is often very expensive and difficult. With effective strategies and measures we can restrict and limit their spread:
a) primarily by preventing entry into the country (restriction of trade in potentially invasive organisms, customs inspections, quarantine),
b) with early detection and timely removal (before flowering, suppression of smaller, initial populations),
c) preventing and limiting the spread (washing of work machines, appropriate handling of excavated soil, greening the open areas),
d) to regular control of already widespread species (mechanical, chemical, biological; removal of entire plants with root system, regular mowing).
The control of invasive non-native species is the duty of the land owner, while the cleaning of public areas is carried
out by the economic public service. Land owners are obliged to control invasive plants from the genus Ambrosia in Slovenia,
which is regulated by the Decree on measures to control harmful plants from the genus Ambrosia (Ur. L. RS, no. 63/10).
For all other non-native species, prevention and control is recommended.
Solidago species are perennials growing from woody caudices or rhizomes.
Their stems range from decumbent (crawling) to ascending or erect, with a range of heights going from 5 cm to over a meter.
Most species are unbranched, but some do display branching in the upper part of the plant.
Goldenrods have become invasive species in many parts of the world outside their native range, including China, Japan, Europe and Africa.
Solidago canadensis, which was introduced as a garden plant in Central Europe, has become common in the wild, and in Germany is considered an invasive species that displaces native vegetation from its natural habitat.
The flowers are small, cream or white, produced in erect racemes 6–15 cm long in late summer and early autumn.
Japanese knotweed has hollow stems with distinct raised nodes that give it the appearance of bamboo, though it is not related.
While stems may reach a maximum height of 3–4 m each growing season, it is typical to see much smaller plants in places where they sprout through cracks in the pavement or are repeatedly cut down.
This species is listed by the World Conservation Union as one of the world's worst invasive species.
It is a frequent colonizer of temperate riparian ecosystems, roadsides, and waste places. It forms thick, dense colonies that completely crowd out any other herbaceous species and is now considered one of the worst invasive exotics in parts of the eastern United States.
Common ragweed is the most widespread species of Ragweed in Slovenia. It is an invasive North American annual plant that has been
intensively spreading in Europe in the last few decades. It can grow up to two meters high. The leaves are transformatively different,
twice pinnately divided, the petiole is covered with sparse and protruding hairs. It blooms from July to October, and the seeds ripen
in August. It thrives on sunny and gravelly sites, along railways, highways, rivers and poorly maintained abandoned agricultural land.
It brings additional costs and economic damage to agriculture. Its spread is suppressed by pulling when the plants are 10 to 20 cm
high. For larger plants and larger areas, mechanical and chemical control is required. Mowing is only effective with regular
repetitions. Chemical control with herbicides is only permitted with certificates and permits in a way that is not harmful to
people and the environment. Common Ragweed pollen is an allergen. Gloves and full body clothing should be used during removal
to protect against skin irritation. If the removal takes place during the flowering season, a mask and protective glasses
should also be used to protect against pollen. It is better to remove flowering plants in the afternoon, as the pollen is
mainly released in the morning.
Reports about the suspected presence of Ragweed and non-implementation of measures are handled by phytosanitary inspectors.
Based on the findings during the inspection, the inspector informs the owner of the land of the prescribed phytosanitary measures
and sets a deadline for their implementation.
The tree of heaven is a fast growing tree native to northeastern and central China. It is known for its ability to thrive in harsh
conditions, including polluted soils and disturbed areas.
In Slovenia, it was planted as an ornamental tree and for the purpose of afforestation of infertile land.
It grows up to 20 m in height, rarely more. It is a dioecious species, it blooms in late spring, the fruits ripen in autumn.
It is carried over long distances by wind, watercourses and other vectors of spread. It quickly occupies degraded and neglected
areas, but it is not a long-lived species. It also reproduces via root growths. With its rapid growth, it is displacing native
species. It secretes allelopathic compounds with a herbicidal effect into the soil. It is not problematic on maintained surfaces.
When removing, we must use protective equipment due to the toxicity of the plant, as the plant juice can cause dermatitis,
and in exceptional cases also myocarditis.
The plant must be removed as soon as it appears on the land.
It is necessary to remove female trees from plantations to prevent the formation of new fruits.
The easiest way is to dig up young plants, as smaller trees are most efficiently removed with the help of a special tree pulling tool.
For larger trees, ringing is suitable, otherwise a strip of bark is removed around the entire perimeter of the tree.
This partially destroys the conduction system and causes the slow death of the tree.
Cutleaf coneflower is a robust herbaceous perennial plant that can grow up to 3 metres. Rudbeckias are native to North America. Because of their attractive appearance, they began to be cultivated in Europe as early as the beginning of the 17th century. Today, Cutleaf coneflower is found scattered throughout almost all of Slovenia. Due to its attachment to moist habitats, it often occurs along streams and rivers, where in dense stands it can prevent the growth of native riparian plants. It is a herbaceous perennial that has durable rhizomes in the ground. The color of the flowers is similar to Jerusalem artichoke (Helianthus tuberosus), which has larger pieces. With its broad adaptability to various environmental requirements and extremely fast growth, it is more competitive than many species that thrive natively in our country.