Dendrochronology was used to study 25 years of rockfall activity on a forested slope at Täschgufer, Täsch (Swiss Alps). We introduce a new approach by evaluating the initiation of callous tissue and resin duct formation after rockfall occurrence to determine the  seasonal timing of events.The approach used for this investigation proves to be a useful tool for analyzing differences in intra-annual rockfall activity on forested slopes. In the case of data available on the different growth phases within the vegetation period of the selected tree species at the study site, results on the seasonal timing of rockfall activity can even be given with almost monthly resolution. However, for rockfall occurring within the dormant season, tree-ring analysis needs to be completed with direct observations on the site.