Coolsingel, Rotterdam: preserving historic plane trees with TreeParker

During the redevelopment of the Coolsingel, Rotterdam chose to retain its distinctive plane trees despite extensive works and limited underground space. With the help of the innovative TreeParker soil cell system, a sustainable tree pit was created that both protects the trees and supports the renewed urban boulevard.

The Coolsingel has been the iconic heart of Rotterdam for decades. In 2017, preparations began for a large-scale redevelopment in which the boulevard’s traffic function would make way for a more attractive and greener public space. With the new design, the Coolsingel is intended to offer visitors a warm welcome at any time of day and in every season. The municipality’s ambition was clear: to transform the Coolsingel from a traffic artery into a high-quality urban boulevard where pedestrians, cyclists and quality of stay take centre stage.

One of the key challenges was the preservation of the existing rows of trees. Mature London plane trees lined the Coolsingel, some of which have been part of the streetscape since the 1960s. Arboricultural investigations showed that these trees represent significant spatial and cultural-historical value. At the same time, the construction works, combined with the presence of metro, tram and utility infrastructure, would place considerable pressure on their rooting environment.

During the redevelopment, it was reported in 2019 that the Coolsingel would accommodate 250 trees in its new layout, including 87 new trees. The new trees were all planted within the TreeParker system. For the existing trees, additional growing space was created on the street side wherever possible. The compacted subsoil was excavated and replaced with TreeParker modules 60 centimetres high, connected to form a width of 3 metres and installed along the full length of the tree zones. The system was filled with tree soil, covered and finished with the new paving.

TreeParker is an underground tree pit system that provides trees in urban environments with sufficient space to grow healthily. The strong, modular structure is installed beneath the paving and creates a large volume of rootable growing space. This space can be filled with a soil composition tailored to the tree species. In addition, the system ensures improved water and oxygen supply and greater stability for the tree. Root growth is also guided in the right direction using Tree Root Guiding, preventing root heave. Cables and utilities can moreover be easily integrated into the open, modular structure. In this way, the plane trees on the Coolsingel were given ample space to continue growing, without compromising the new design and intensive use of the boulevard.

It became clear during the works that the roots quickly managed to find the additional growing space. When installing lighting columns, the soil cell systems installed in 2018 were opened up. In less than a year, the roots had already begun to grow extensively into the new growing space. A promising result, even before the redevelopment had been completed. “We know what this system can do for trees. But perhaps we are seeing the results even sooner than expected,” said the Coolsingel project manager at the engineering department of the Municipality of Rotterdam. In April 2021, the renewed Coolsingel was officially opened.

The Coolsingel regularly serves as the venue for large-scale events, festivals and celebrations, attracting tens of thousands of visitors and football supporters. During such gatherings, the public space is subjected to intensive use, with large crowds often remaining and jumping on the same location for extended periods. Nevertheless, the TreeParker soil cell system beneath the paving continues to perform in a stable and reliable manner. Thanks to its construction, designed to withstand the heaviest traffic loads, both the tree pit and the trees remain optimally protected, even under the most intensive conditions of use.

The success of the carefully considered approach on the Coolsingel remains visible in the long term. In 2026, years after completion of the project, the plane trees still stand healthy and vigorous along the boulevard. Every day, the trees make an important contribution to the urban climate by providing cooling shade for residents and visitors. At the same time, they reinforce the green, monumental character of the boulevard and form an indispensable part of Rotterdam’s attractive streetscape.

This project demonstrates how existing mature trees can be successfully integrated into complex inner-city developments. By consciously selecting optimal underground tree pits, not only is the green character of the Coolsingel preserved, but the benefits of mature trees are safeguarded as well. From shade, climate adaptation and biodiversity to a high-quality public space experience.