Beyond the list: Rethinking the urban tree
What makes a tree future-proof is not its origin, but how it responds when conditions are far from ideal.
In discussions about climate-adaptive planting, the search for the “right” species often leads to lists, rankings and fixed preferences. But according to Marko Mouwen of Tree Nursery Ebben, that approach misses the point entirely. The performance of urban trees cannot be reduced to a top ten. Instead, it depends on a detailed understanding of spatial constraints, soil composition, water dynamics, light conditions and genetic background. What matters is understanding what a tree is made of, and what it requires both above and below ground to perform in the city.
Mouwen believes the focus is still too often on trends, such as lists or a strict preference for native species, while this is simply not realistic in an urban context. “It is not realistic to plant an entire city with ten species simply because they are native. That may work in rural settings, but not in urban conditions. Cities require a broader palette of species. Not because origin is unimportant, but because it needs to be understood technically. If you understand where a tree comes from, you understand why it performs in a particular location. That is why I do not offer a top ten, but examples that support my argument.”
Ecology through diversity
A broader palette does not automatically mean an increase in exotic species. Rather, it points towards functional diversity. In this context, ecology is not something that can be designed directly, but something that emerges from well-considered choices.
By varying species and genetic profiles, planting schemes become more resilient and less vulnerable to pests and diseases. At the same time, they support a wider range of ecological functions. Even within a single genus, diversity can make a significant difference. Several lime tree varieties, for example, can collectively provide a longer flowering period and a broader range of benefits for insects and birds than a single species.
Recovery capacity as the key
Urban trees are rarely exposed to stable conditions. Fluctuations in moisture, temperature and soil quality are the norm rather than the exception. In this context, the ability to recover becomes a defining characteristic.
Resilience, understood as the capacity to tolerate stress, repair damage and resume growth, is therefore a key selection criterion. A tree’s long-term value lies not in its ideal performance under optimal conditions, but in how it behaves when those conditions inevitably deteriorate.
Elm trees
The elm is a clear example of this principle. Decades of breeding have resulted in varieties that are resistant to Dutch elm disease as well as urban stress. In addition to hybrids, selections such as Ulmus pumila ‘Select’, Ulmus ‘San Zanobi’ and Ulmus ‘Frontier’ have proven to be reliable urban performers. They combine tolerance to drought and heat with strong growth and high disease resistance. What makes the elm particularly valuable, according to Mouwen, is its exceptional recovery capacity: it can lose its leaves and flush again multiple times a year. This regenerative ability makes it highly suited to the urban environment.
Flexibility in an uncertain climate
Alongside recovery capacity, flexibility is essential, the ability to cope with uncertain conditions before damage occurs. In an increasingly unpredictable climate, selecting trees based on a single future scenario is no longer sufficient. According to Mouwen, this calls for genetically diverse, adaptable species that can respond to conditions we cannot yet fully predict. Hybrids play an important role in this regard. A notable example is xSycoparrotia semidecidua, a cross between Parrotia persica and Sycopsis sinensis. It combines strong wood quality and stress tolerance with flexibility and a semi-evergreen character. “As in the animal world, hybrids often benefit from greater genetic diversity and therefore increased robustness,” Mouwen explains. That said, Parrotia persica itself remains a reliable choice for urban planting, thanks to its tolerance to drought, heat and air pollution.
Built for extremes
In urban environments, water is rarely balanced: it is either too much or too little, often within short periods of time. Due to paving and limited rooting space, trees are exposed to significant fluctuations. This calls for a different perspective on climate resilience. “We need to move away from thinking primarily in terms of frost, and instead focus on extremes such as drought, heat, waterlogging and reflected light.” Hybrid maples respond well to these conditions. Acer × freemanii ‘Autumn Blaze’, a cross between Acer rubrum and Acer saccharinum, combines rapid growth with a strong branch structure and tolerance to fluctuating soil moisture. Acer truncatum ‘Norwegian Sunset’ also demonstrates how breeding can result in heat-tolerant foliage and a stable crown structure.
Strength through variation
Not all suitable urban trees are hybrids. Species such as Quercus imbricaria and Zelkova serrata have proven themselves over many years in urban environments. They are tolerant of drought, heat and air pollution, and contribute to a diverse planting palette. “As long as you diversify, there is little cause for concern. The greater the diversity, the lower the risk of pests and diseases.”
A pragmatic approach to urban greening
While visual qualities remain important, they should not be the primary driver in species selection. In urban settings, factors such as resilience, robustness and ease of management are more critical. Trees such as Tilia mongolica ‘Buda’ illustrate how these qualities can be combined with a refined appearance. Compact, adaptable and structurally sound, they are well suited to the constraints of the built environment.
Ultimately, successful urban planting requires a pragmatic approach. It is not about following trends or adhering to fixed preferences, but about making informed decisions based on performance, diversity and long-term risk.
Or, as Mouwen puts it: the best urban tree is not the most attractive one today, but the one that remains healthy decades from now.
Find out more: Ebben Tree Nursery