• This week, the tree maintenance team from Aachen's municipal services is planting six trees in Leydelstraße in a so-called just-in-time measure.

• New trees are replanted in the same location shortly after old, diseased trees have been felled.

• In Leydelstrasse, the team can thus replace six robinia trees with six amber trees after extensive earthworks.

Planting a tree is more time-consuming than many people think. But planting a street tree where an old, diseased tree was standing the day before requires precise adherence to many different, important steps. In order to remove diseased trees from the streets in the shortest possible time and replace them quickly with new trees, the tree maintenance team of Aachen's municipal services has once again initiated a "just-in-time measure" in Aachen's city center.

Six robinia trees are affected in Leydelstraße: Bark damage impaired the stability of the trees, which are around 60 to 70 years old.

Because they were no longer safe for traffic, they were professionally felled by the tree care team at the start of the project. Now, on the following day, colleagues begin to prepare the empty tree slice for replanting. The roots are milled out, the used soil is excavated and the edging of the site is repaired in places. Additional aeration also ensures sufficient gas exchange so that no waterlogging or rotting can occur. The employees of the tree planting team add a soil activator to the soil to ensure sufficient microorganisms in the soil. A starter fertilizer is also required so that the trees sprout in the root area first before they grow within the tree crown.

Meanwhile, the tree planting team from Aachen's municipal services is preparing to plant six new amber trees; these are particularly resistant to heat and drought and their foliage turns an attractive red-yellow in the fall. A watering ring is placed around the planted trees. In dry, hot periods, a tree needs up to 200 liters every 14 days. Finally, tensioning straps are attached between the installed tripod anchoring and the tree so that the young tree is stable.

A "decade of urban trees"

Trees in street areas are more exposed to climatic changes than trees in green spaces, for example. Among other things, a lack of space, exhaust fumes, drought and heat put a strain on trees. However, a city needs many healthy street trees that provide shade, improve air quality and enhance the quality of life. In order to meet the challenges of climate change, Aachen needs a "Decade of Urban Trees", emphasized Heiko Thomas, Head of Climate and Environment, City Operations and Buildings of the City of Aachen. "We lose more trees in Aachen every year than we plant. We therefore need to look after the existing trees and plant more trees at the same time."

Increasing new plantings per planting season

The tree planting season runs from October to March. "During this time, the trees tolerate the so-called planting shock much better than in the warmer months," explains Michael Speck, tree planting team leader at Aachen's municipal services. Pre-grown trees from the nursery are planted; the amber trees are already eight to ten years old.

Failure rate for newly planted trees

The extensive preparatory work means that the newly planted trees can develop particularly well. Nino Polaczek-Keilhauer, tree care team leader at Aachener Stadtbetrieb, explains: "We at Stadtbetrieb are very well positioned thanks to our expertise and the available technology, which has meant that we have no longer had a significant failure rate when planting new trees in recent years." From the next planting season, a suction excavator will facilitate the just-in-time measures. This will gently suck up the old soil after felling.