But Rolf Dung (City Council Bonn) is giving the all-clear: This process is happening regularly. Every three to four years sycamore trees are shedding their bark and losing it. The continuous dry spell has nothing to do with it.

„The shedding of the bark is a reaction to the trees’ girth growth“, says Dung. „Over the years the girth creates a tension in the lower bark layers.“ At some stage, the tension gets so strong that the bark gets pushed out. „Other tree types do the same thing but a lot more discreetly, because they only lose small bark parts. The whole process is a natural occurrence which is repeated every few years.“

Bonn counts around 30,000 trees along the streets. About 4,200 of those are sycamore trees. This type of tree was a cross between an Asian and an American tree type.

Even though the bark shedding is not caused by the dry spell: Many street trees are suffering from dehydration. Residents should water the trees in their neighbourhood, suggests Markus Guhl, director of the Federal Association of Tree Nurseries in Germany. „If a street tree is lucky, it can avail of about twelve cubic meters of good earth. Underneath there’s only rubble and rocks.“ The tree cannot stretch its roots further to get a sufficient amount of water during a continuous dry phase. But how much water does a 20-meter-tree need? „About 100 litres“, says Guhl. „But even 20 litres - two filled watering cans - can help a bit. Better a little bit of water than none.“

The Association for environment and nature protection in Germany (BUND) recommends to water street trees once a week with eight to ten buckets of water.

Original text: Jana Henseler

Translation: Mareike Graepel