The city centre of Goirle in Brabant has traditionally had a green character that emphasises the charm of the village. This green character came under pressure during a large-scale renovation of the centre, which simultaneously involved the construction of an underground car park. These works required the felling of many trees, leading to concerns about preserving the green landscape. The municipality of Goirle set as a precondition that new trees should be replanted, to maintain the balance between renewal and greenery. However, replanting in open ground proved impossible due to the presence of the parking garage directly under the centre.
After extensive consultation with the project developer and urban planning agency KuiperCompagnons from Rotterdam, it was decided to place the trees in large, specially designed containers. The municipality reserved a budget for this and KuiperCompagnons incorporated the wishes and requirements into their design. Robust steel flower pots measuring 3.5 by 2 metres were chosen, executed in classic red to fit in with Goirle's village character. Various types of trees were planted in these containers, including trident maples, Japanese walnut trees and Chinese varnish trees, each contributing to the biodiversity and aesthetic value of the town centre.
Maintaining trees in containers requires special care and attention, as these trees cannot get their water and nutrients directly from the soil. To meet these needs, the trees in Goirle were connected to an advanced water and nutrient system, connected to a break tank on the roof of the car park. This system ensures a constant supply of water and nutrients. In addition, a static water reservoir consisting of a 20 cm deep layer of clay granules, soil and filter cloth was constructed at the bottom of the tree boxes. This reservoir acts as an emergency supply, providing the trees with temporary water in case of system failure.
Besides an adequate water supply, a special substrate was developed that promotes water absorption and contributes to the health of the trees. The bins are also insulated with PE foil to prevent the roots from drying out due to heat radiation. As an additional measure, the tree boxes were planted with lady's mantle (Alchemilla mollis), a plant that curls up its leaves when the soil is too dry. This provides a visual indication of possible problems with the watering system and allows managers to intervene quickly if necessary.
Thanks to these innovative solutions, Goirle's green character is preserved and residents and visitors can enjoy a lively and green city centre, even with the presence of a modern underground car park. The combination of aesthetics, sustainability and technology makes this project a model for other cities facing similar challenges.
