Invasive plants in the EU Part 4: Climbing plants (vines)

Union list of invasive species

There are around 12,000 alien species in the EU. A small number of them require special attention as they can endanger the populations of native species.

The EU regulation on the prevention and management of the introduction and spread of invasive alien species is intended to prevent these species from spreading and to enable a rapid response when the first signs of spread appear. The exact species concerned are listed in the “Union list”. Of the 88 invasive species listed, 40 are vascular plants. In this series’ previous articles, we have presented shrubs and trees, aquatic plants and grasses; today we are looking at vines. Make sure to also check out our articles about invasive perennial and annual herbaceous plants.

Cardiospermum grandiflorum, the balloon vine

As an ornamental plant, Cardiospermum grandiflorum from Central and South America has spread almost worldwide. However, its small white flowers and attractive fruits should not obscure the fact that the woody shoots can form massive carpets that can completely overgrow trees 10-20 meters high. As a result, they obscure the habitat below and their weight can also lead to the collapse of overgrown structures. Furthermore, wild and grazing animals are prevented from moving or migrating freely.

Lygodium japonicum, the Japanese climbing fern

Lygodium japonicum is native to eastern Asia. The plant forms fronds on its creeping rhizomes, which can grow up to 30 meters long and display climbing traits. The species produces very small spore capsules that can easily be spread via clothing and luggage, but also in potting soil. The Japanese climbing fern is well adapted to the cold and its spores remain viable despite frost. Nevertheless, it prefers warm, humid locations to spread. In North America, the species is already changing the intensity and extent of fires, as it allows flames to climb quickly into the crowns of trees.

Pueraria montana, Kudzu

Pueraria montana, also known as Kudzu, belongs to the legume family and originates from East Asia. According to the IUCN, it is one of the 100 most aggressive invasive neophytes, as it can completely cover and destroy existing vegetation in just a few years. In addition to the perennial, strong lianas, which can grow up to 20 meters per year, it forms root tubers as survival organs. These can reach lengths of 2 meters, diameters of 18 to 45 centimeters and a weight of 180 kg. It colonizes gardens, road embankments and lakeshores. In Switzerland and Italy, Kudzu can already be found in warm habitats.

Celastrus orbiculatus, the round-leaved tree shrike

Once introduced as an ornamental plant, the round-leaved tree shrike (Celastrus orbiculatus) is still available here and there despite a trade ban. It is spread by improper disposal of plant parts and berry-eating birds. If the liana can climb up trees, it grows up to 12 meters high. Otherwise it forms a very dense, ground-covering tangle. When still young, it provides massive shading of the vegetation and increases the risk of young trees breaking. As it grows thicker, the tree strangler exerts increasing pressure on its supporting trees and can “strangle” them.

Humulopsis scandens, Japanese hop

Japanese hop (Humulopsis scandens) was a popular ornamental plant in many countries for greening trellises and fences. It naturally colonizes river courses quite quickly, but its new dispersal routes are determined by human activity. Once it has gained a foothold, it is able to change habitats structurally and functionally by overgrowing and shading, thus reducing species diversity. In particular, reedbeds and willow fringes are threatened by Japanese hops. The species is an annual, which consequently leaves the ground open at the end of the growing season, making it susceptible to erosion by water.

Persicaria perfoliata, the knotweed

Persicaria perfoliata is an annual to perennial liana and can climb up to 8 meters high. The species is not yet established in Europe, but would find good living conditions in forests and disturbed areas. Its seeds are readily eaten by animals, which enables it to spread quickly. In the USA, it forms dense mats that cover the vegetation and cause the underlying species to die. The forestry industry there is already reporting economic damage, as are fruit growers, tree nurseries and the tourism industry.

Documenting the spread

If you identify plants with Flora Incognita and allow access to your location, your find will become part of a scientific data collection that enables our scientists to research the distribution of species in time and space. You can read about our research work here. This data can also be used to plan and implement nature conservation management measures quickly and effectively. Thank you for your help!

Attention! The species on the Union list may not be intentionally introduced into the territory of the EU, kept, bred, traded, used, exchanged, used for reproduction or released into the environment!

Featured image: knotweed (Mile-a-minute-weed (28816287065).jpg) by Katja Schulz. CC BY 2.0.