Lime trees struggle with the heat: Czech cities search for climate-ready trees

The classic small-leaved lime, planted along the streets and squares of Czech towns for decades, is increasingly struggling to cope with summer heat and drought. Because of climate change and the urban heat island effect — where city temperatures can run several degrees higher than in the surrounding countryside — landscaping specialists are being forced to rethink the standard palette of tree species used in urban plantings.

Why old favourites no longer work

According to Miroslava Florjánová, a climate adaptation landscaping specialist with the Partnerství Foundation's Adapterra programme, it is no longer enough to choose trees simply because they grow naturally in the Czech Republic. What matters far more is whether a tree will be able to thrive in the conditions cities are expected to face several decades from now.

The issue lies in what are known as vegetation zones — areas with similar climates and characteristic sets of plants. As warming and shifting precipitation patterns take hold, the boundaries of these zones are moving: land that, climatically, matched a cooler zone half a century ago may today resemble conditions typical of much warmer regions. In cities, the situation is further complicated by a lack of water and root space, compacted soil, and, in winter, salt damage from de-icing chemicals.

For inspiration, specialists are looking to warmer parts of Europe. The small-leaved lime, for instance, is increasingly being replaced in new plantings by the more drought-tolerant silver lime. Other promising species include the Japanese pagoda tree, honey locust, field maple, downy oak and European hackberry.

Prague searches for the trees of the future

The "Climate Trees for Prague" project is trying to identify species that will genuinely take root in Czech cities. The first experimental plantings appeared in spring 2024, with the project set to run through roughly 2040. Prague's streets are currently testing select varieties of oak and elm, narrow-leaved ash, honey locust, common almond, Italian maple and Chinese ash. The first interim results are expected in about six to eight years, and the findings should prove useful not just for the capital — Brno faces the same challenge, as do, increasingly, other Czech cities.

Choosing the right species, however, is only part of the solution. Even a heat-resistant tree won't survive if it's given a few cubic metres of compacted soil between the road and the pavement, with all the surrounding rainwater simply draining into the sewer. That's why some Czech cities are rethinking their entire approach to street reconstruction.

A telling example is Roudnice nad Labem, where landscape architect Martina Imramovská, together with a colleague, persuaded the city council that street renovations should not only include more trees, but also a redesigned rainwater drainage system. According to Martin Ander, head of the Partnerství Foundation's Adapterra programme, the results are already visible in the town and are noticeably helping to prevent overheating. Instead of rainwater being rushed straight into the sewer system, it is now channelled into green strips along the streets — trees draw moisture directly from their immediate surroundings, grow better, and provide more shade and cooling in summer. Úvaly, near Prague, has taken a similar path, gradually expanding its green spaces and redesigning public areas to capture rainwater.

Trees versus historic squares

The situation is even trickier in historic town centres. Stone squares heat up considerably in summer, but heritage protection rules limit how much greenery can be added. A dispute of this kind arose in Jihlava, where the urban environment department tried to add trees to historic squares, while opponents cited concerns about preserving views of monuments and the risk that roots could damage underground historic structures. A similar conflict occurred in Třebíč during the reconstruction of Karlovo náměstí, where the number and placement of trees on a largely stone-paved space was likewise disputed.

Despite such conflicts, cities and heritage authorities are increasingly finding compromises — as happened recently in Znojmo and Kroměříž.

Greenery isn't just for the streets

Cooling a city doesn't only come from parks and street plantings. In Plzeň, the modernisation of the Slovany tram depot included the installation of an extensive green roof covering around 1,400 square metres. The idea wasn't obviously appealing at first: specialists from Plzeň's urban concept and development department had to convince the transport company that a huge roof needn't intensify the heat island effect around the building — on the contrary, it could help retain water and cool the surrounding area.

The project drew on data from the Partnerství Foundation about the capacity of green roofs to retain rainwater. Excess moisture collected at the Plzeň depot is even used to wash the trams — as Martin Ander notes, it's an excellent, if still rare, example of good practice in the Czech Republic.

Read also: Prague metro: map and tickets

Source: ekolist.cz