The Character of Public Green Spaces in Ljubljana

Public spaces play a vital role in shaping and enabling a high quality of life for city residents, which makes their proper management essential. Sound planning is the foundation of all urban green areas.

Greenery is not merely about creating a pleasant atmosphere or adding beauty to a concrete environment. It plays a crucial role in mitigating climate change, increasing biodiversity, purifying and humidifying the air, slowing stormwater runoff, and reducing the risk of flooding.

In light of these important functions, the Association of Ornamental Plant Growers of Slovenia (ZPORS) organized a professional tour of public green spaces in Ljubljana. The tour was attended by representatives of municipal service companies and municipalities responsible for green space management, representatives of companies involved in landscape management in various capacities (including Arboretum Volčji Potok and Tisa d.o.o.), as well as ornamental plant growers from across Slovenia.

Challenges of Public Green Spaces in Ljubljana

Far too many public areas are still designed as “instant” landscapes — lawns with a single tree or shrub planted in the middle. At the roundabout between Kolodvorska Street and Ilirska Street, where a London plane tree (Platanus × acerifolia) is combined with various perennial species, we discussed the importance of such mixed plantings.

It was emphasized that combining trees with perennials is highly beneficial, both in terms of soil coverage and improved soil aeration. At the same time, it was noted that perennials should not be planted directly against tree trunks. A narrow, unplanted margin should be maintained around the base of the tree to ensure easier access and better maintenance. This is particularly important in the first years after planting, when trees are still establishing their root systems.

A perennial planting in front of the courthouse building demonstrates how little maintenance such plantings require – especially when the species are carefully and appropriately selected.

Avenues Should Be Designed by Experts!

The process begins with selecting the right species. At the area between Bavarski Dvor and Kersnikova Street, we observed rowan trees (Sorbus species) planted in pots – clearly an inappropriate choice for urban planting.

In practice, tree selection is often based on web information especially when the investor has limited familiarity with plants. In books, or online, a species may be described as having certain characteristics that appeal to the investor, who then chooses it without considering site-specific conditions.

We highlighted the importance of coordination in practice, ensuring that the perspectives of the investor, the contractor, and the maintenance team are aligned when planning and establishing a planting.

Are Ljubljana’s Parks Prepared for Climate Change?

It is essential to use plant species in urban plantings that are sufficiently adaptable to diverse climatic challenges. Perennials are certainly a good example of such adaptable plants. By selecting the best available cultivars — which are constantly being improved — cities can effectively address the impacts of climate change. This makes it crucial for planners to stay in close contact with experts who work directly with plants, ensuring that the most suitable and resilient varieties are used. Collaboration between planners and horticultural professionals is the key to accessing and applying the best available plant material.

Climate change also brings new diseases and pests. Therefore, species and cultivars must be carefully chosen for their tolerance, or ideally resistance, to these threats. In Ljubljana, for instance, new plantings still sometimes include horse chestnut (Aesculus hippocastanum), despite long-standing knowledge of problems caused by the leaf miner (Cameraria ohridella) on this species.

Why Is the Tree on Your Street Struggling?

There are many factors in urban environments that can cause trees to decline. It is essential to ensure optimal growing conditions when planting a young tree. Recently, trees are planted too deep, which often leads to rapid decline and even death.

It is also highly beneficial to protect young tree trunks at planting from physical damage or sunscald using materials such as jute or reed. In practice, reed often performs better over time, as jute can eventually become embedded into the bark. Sunscald and similar damage can harm the tree’s bark and, if repeated, may contribute to its decline.

Without Expertise, Ljubljana’s Residents Are at a Disadvantage

The true reflection of any city is its overall planning and design. High-quality management of green spaces contributes significantly to the city’s overall appearance and functionality. This is why careful design and professional implementation of green spaces are so important. Expert planning and maintenance can sometimes even partially compensate for less-than-ideal original designs.

During a visit to Argentine Park, we observed that the perennial planting there was installed without a clear purpose or broader design concept. Nevertheless, it still adds visual interest to the area and provides habitat for bees and other wildlife – a contribution that is especially valuable in today’s rapidly urbanizing environment.

Text by prof. dr. Gregor Osterc

Cover photo: Slovenia.info