On the lawns of the capital's Petržalka district along the streets Pankúchova and Mamateyova, despite the summer drought and heat, pajaseň žliazkatý (Ailanthus altissima, tree-of-heaven) is actively spreading. This Asian woody weed is considered one of the most aggressive invasive species in the world, and attempts by municipal workers to get rid of it often lead to the opposite result.
The problem attracted the attention of the district environmental commission after a local resident appealed through deputy Lenka Milincká (Lenka Milincká). Near her house, municipal workers cut down three mature trees, but instead of a clean lawn, the area became covered with a dense carpet of young shoots, which quickly spread to neighboring streets and container sites.
Why Ailanthus is called the “tree from hell”
Ján Šeffer (Ján Šeffer), director of the applied ecology institute DAPHNE, says that Ailanthus altissima (tree-of-heaven) poses a serious threat to local flora and urban infrastructure. The plant has powerful toxic effects:
- The sap of the leaves and bark can cause allergic reactions and dermatitis in people.
- The roots and fallen leaves release special suppressive substances — allelopathic compounds (in particular, ailanthone), which poison the soil and prevent any other grass or trees from growing nearby.
- The tree is incredibly hardy, tolerates severe drought, urban pollution, and easily sprouts right in cracks or joints of sidewalks.
- One mature self-seeded tree can produce up to one million seeds annually.
Hostages of the law: cutting is mandatory, but it doesn’t help
According to Slovak legislation and nature protection rules, landowners and managers are obliged to purposefully destroy invasive alien species to prevent them from spreading to new areas. Local authorities in Petržalka regularly carry out cutting of such trees, especially on school and kindergarten grounds.
But simply cutting the trunk does not solve the problem and sometimes only makes it worse. The head of the local environmental protection department, Adrián Ševeček (Adrián Ševeček), explains that the tree’s powerful root system perceives cutting as a survival signal. The underground part of the plant begins to massively produce protective shoots (sprouts), turning the lawn into impenetrable thickets.
How they fight the weed and what residents should do
Traditional control methods in urban conditions are very limited. For example, Petržalka has a special status “Zones without pesticides” (Zóny bez pesticídov), which prohibits the mass use of toxic chemicals to destroy plants near residential buildings.
To increase the effectiveness of clearing, municipal workers implement a comprehensive approach — immediately after cutting the trunk, they perform deep stump milling and mechanical removal of the root system.
If you notice active spread of invasive plants near your home, you can submit an official request to the district office through local platforms for submitting appeals and complaints, so that municipal services include the area in the sanitation cleaning plan. More about the situation in the capital can be read in the article by Bratislava News.
