In Rome, ailanthus altissima, commonly known as the tree of heaven, carries a controversial legacy. A Jesuit priest, Pierre Nicolas Le Chéron d’Incarville, is credited with introducing the tree from China in the 18th century, a time when curiosity and commerce carried such plants across continents. Today, the species is viewed in Rome as an invasive presence, provoking strong opinions and drawing ongoing media attention. The tree has colonized many parts of the city, thriving where other vegetation struggles to survive.
Ailanthus is not a harmless urban addition. It grows aggressively, resists easy removal, and presents a persistent challenge for city managers. In an interview with El País, Mario Tozzi, a respected Italian geologist and naturalist, explains that the plant arrived in Italy by mistake. It was once thought to shelter silkworms, a claim that proved unfounded. The tree multiplies rapidly, tolerates heat and humidity, and often colonizes asphalt, undermining nearby plants and infrastructure. The problem remains stubborn and hard to control.
impossible to destroy
Tozzi’s varied roles underscore the tree’s tenacity. From 2006 to 2011, while leading a national park in the Tuscan archipelago, a long-term campaign to remove the tree faced ongoing obstacles. He later faced a similar challenge at Ancient Appia Park in Rome starting in 2013. The plant appeared everywhere, showing a distinct preference for green spaces, and its resilience made removal a complex task. The expert notes that eliminating it remains exceptionally tricky.
Ailanthus is more than just a plant. It adapts to nearly any surface, thrives in warm climates, endures drought, and tolerates urban pollution and climate shifts. It reproduces prolifically, with each tree capable of producing hundreds of seeds, and damaged roots can sprout new shoots up to 15 meters from the parent plant. Originating in China, the tree is not part of the local wildlife diet, including goats, which avoid it likely due to its strong odor. It even serves as a habitat for other invasive species, such as the brown marmorated stink bug and certain wood-boring insects, a pattern researchers highlight as observed in studies by National Geographic.
Beyond ecological concerns, the issue has become a civic matter. The spread of ailanthus disrupts native ecosystems and sparks debate among residents about protecting city vegetation. In areas with uneven road maintenance, the tree is increasingly recognized as a threat to safety and visibility. City officials report rising concerns as ailanthus pushes into public spaces and roadways.
limits visibility
The plant appears throughout Rome but concentrates in neglected zones such as abandoned lots, old factories, and along roadways. The Rome Department of Environmental Protection is frequently involved in interventions there, but the danger is real: rapid growth can obscure sightlines and affect traffic signals and intersections. Local authorities emphasize the practical risk of reduced visibility and compromised road safety.
Some residents expressed frustration on social networks about the swift spread of ailanthus in central areas like Muro Torto, describing it as a forming forest that encroaches on the street. Posts from the Light of Rome account reflect public focus on the issue. Not everyone shares the same view; some argue that ailanthus has historically contributed to the landscape by providing biodiversity and shade. Protests against tree removal have occurred in various neighbourhoods.
The City Council clarifies that the solution is not straightforward. European regulations limit certain herbicides, which complicates rapid eradication. Glyphosate spraying, effective in other regions, is constrained by rules, so the city relies on endotherapy and selective treatments in large facilities where feasible. The aim is to protect archaeological remains while keeping growth in check.
When herbicide use is not feasible, mechanical removal and regular pruning become the primary approaches. Continued maintenance and monitoring remain the practical path to managing new growth while preserving the city’s historic and cultural assets.