Date Palms and Pomegranates Grow Wild in Brussels

A date palm sprouting from a crack between stones. A pomegranate shrub taking root in a roadside verge. These are not scenes from Andalusia or Sicily — they are happening today in Brussels, where climate change is quietly rewriting the botanical map of Belgium’s capital.

According to VRT NWS, Mediterranean plant species are now growing spontaneously in Belgian cities, a phenomenon that scientists are calling the “Mediterranization” of urban flora. Warmer winters, rising average temperatures, and the urban heat island effect are creating conditions that allow southern European species to survive and reproduce in what was once a temperate climate zone.

The FloraBru Project: Documenting a Transformation

This botanical shift is being systematically tracked by the FloraBru project, a collaborative initiative between Natuurpunt, Natagora, and Leefmilieu Brussel (Brussels Environment). The project aims to produce a comprehensive atlas of wild plant species in the Brussels Capital Region — the first update in two decades.

As Natuurpunt reports, the first year of surveying in 2024 recorded 1,089 plant species and 43,218 observations across 188 one-square-kilometer survey squares. This represents a dramatic increase from the previous atlas (2003–2005), which documented just 793 species and 37,833 observations.

Roosmarijn Steeman, a scientific collaborator at Natuurpunt Studie, has been at the forefront of these observations. “We see a lot of change,” she told VRT NWS. “I even saw a pomegranate shrub that had grown spontaneously somewhere, because they can now survive the winters here.” She also noted a date palm that had begun growing spontaneously between stones. “That’s how you notice how everything is changing.”

Three New Species for Belgium

The 2024 survey recorded three plant species for the first time in Belgium. Botanist Filip Verloove of Meise Botanic Garden identified three different introduction pathways: Snowdenia polystachya likely arrived via birdseed, Geranium thunbergii is an escaped ornamental plant, and the pomegranate (Punica granatum) likely resulted from discarded food seeds germinating.

Of the 54 species entirely new to the study area in 2024, 80% are non-native, and 89% of those are classified as “incidental introductions” — species that appear occasionally and may not establish permanent populations. Still, the trend is unmistakable.

Why Cities Are Becoming Hotspots for Southern Species

The urban heat island effect plays a crucial role in this transformation. Buildings, pavement, and infrastructure absorb solar radiation during the day and release it at night, making cities significantly warmer than surrounding rural areas. As VRT NWS reported in 2022, temperatures in Brussels can be up to 6°C higher than in the countryside, with extreme differences reaching 10°C on rare occasions.

This urban microclimate creates what researchers call “climate refugia” — pockets where heat-loving species can gain a foothold. The effect is amplified by milder winters, which no longer kill off Mediterranean plants that would have perished a generation ago.

The Rise of C4 Grasses

Another clear indicator of climate-driven botanical change is the expansion of C4 grasses. Unlike the C3 grasses common in temperate climates, C4 grasses can perform photosynthesis with their stomata partially closed, requiring significantly less water. Species like Echinochloa crus-galli (commonly known as barnyard grass) are appearing more frequently in Belgian cities.

“The carbon-4 types can perform photosynthesis while their stomata are closed,” Steeman explained. “As a result, they need less water to produce glucose. These species are really starting to appear more frequently.”

What the ‘Mediterranization’ Means for Urban Ecosystems

The transformation of Brussels’ flora raises important questions about the future of urban biodiversity. While some welcome the additional greenery — C4 grasses provide resilient ground cover in neglected urban spaces — others view species like barnyard grass as unwelcome weeds.

The long-term impact on native plant communities remains uncertain. Some native species may struggle to compete in warmer, drier conditions, while new arrivals may fill ecological niches left vacant by retreating temperate plants. The FloraBru project, which runs through 2026 with the help of citizen scientists, will provide crucial data for understanding these dynamics.

A Visible Sign of a Changing Climate

For residents of Brussels, the sight of a pomegranate shrub or a date palm growing wild is more than a botanical curiosity — it is a tangible, visible reminder that climate change is not a distant future scenario but a present reality reshaping local ecosystems. As Steeman put it, “There’s a kind of ‘Mediterranization’ happening of our flora, especially in the cities.”

The question now is not whether this transformation will continue — the trend is clear — but how city authorities, conservationists, and residents will respond to a changing botanical landscape that is, quite literally, growing before their eyes.