Background report on green alder break at Ommersheim pond

Caption: Barrier at the Ommersheimer Weiher after several branch breaks. Entering the closed area is life-threatening. Photos: Stefan Eins, Municipality of Mandelbachtal. Closures at the Ommersheimer Weiher: Danger from green branch breakage Mandelbachtal, June 24, 2026 As the Municipality of Mandelbachtal has already announced on social media, areas of the Gangelbrunnen recreational facility at the Ommersheimer Weiher had to be closed at short notice due to the danger of green branch breakage. Municipal employees and tree inspector Olaf John are currently working to defuse the hazardous situation at the Ommersheimer Weiher and secure the affected areas. "Even during the work on site, spontaneous branch breaks continue to occur," reports Olaf John. "At first, a cracking sound is heard, immediately followed by the branch crashing to the ground." The affected poplars are in full leaf and appear inconspicuous from the outside. At the same time, branches are breaking off the crowns. The likelihood of breaks is highest in the afternoons. Green branch breakage – also called spontaneous breakage or summer breakage – refers to the sudden breaking off of healthy, fully leafed branches. This problem mainly occurs during extended heat and dry periods as well as during calm wind conditions. The calm wind conditions make the phenomenon difficult for many people to understand. Unlike during storms or thunderstorms, there is often no visible external trigger. The affected trees appear healthy, their crowns are green and densely leafed. Nevertheless, heavy branches can suddenly fail. Particularly in parks and recreational areas like the Ommersheimer Weiher, green branch breakage represents a special hazard. There are various hypotheses about the causes. Among the discussed factors are heat stress, drought stress, and the high load on widely spreading crown branches. Despite numerous observations, it is still not conclusively understood why seemingly healthy branches suddenly fail. Researchers therefore assume an interplay of various factors. With the increasingly longer heat and dry periods of recent years, the topic is increasingly coming into the focus of experts. Trees with large crowns and widely spreading branches are especially affected. Such branches act like long levers and are exposed to high loads. At the Ommersheimer Weiher, the poplar stands in particular are affected. Even on outwardly healthy trees, heavy branches can suddenly break off without any noticeable warning and fall to the ground. The danger is not limited to the park area at the Ommersheimer Weiher. It can occur anywhere large deciduous trees grow – such as in forests, cemeteries, along streets, in residential areas, or at leisure and recreational facilities. The danger can only be predicted to a limited extent. Before breaking, the affected branches show no externally visible damage. At the break points, there is neither rot nor other indications of prior damage. Even regular tree inspections cannot guarantee one hundred percent safety. The municipality asks that barriers and notices on site be observed. The affected areas of the recreational facility remain closed until the securing work is completed. Key information about the closure at the Ommersheimer Weiher Closed: Rear part of the facility at Gangelbrunnen (paths and areas under poplars). Hazard situation: Acute life-threatening danger from unpredictable, spontaneous branch breaks. Open: The gastronomy, the mini-golf course, the pedal boat basin, and the circular path around the pond remain accessible.