Cambial injury has been reported to alter wood structure in broad-leaved trees. However, the duration and extension of associated anatomical changes have rarely been analyzed thoroughly. A total of 18 young European ash (Fraxinus excelsior L.) trees injured on the stem by a spring flood were sampled with the aim of comparing earlywood vessels and rays formed prior to and after the scarring event. Anatomical and hydraulic parameters were measured in five successive rings over one-fourth of the stem circumference. The results demonstrate that mechanical damage induces a decrease in vessel lumen size (up to 77%) and an increase in vessel number (up to 475%) and ray number (up to 115%). The presence of more earlywood vessels and rays was observed over at least three years after stem scarring. By contrast, abnormally narrow earlywood vessels mainly developed in the first ring formed after the event, increasing the thickness-to-span ratio of vessels and reducing both xylem relative conductivity and xylem vulnerability to cavitation. They accumulated in radial groups in a 30° sector immediately adjacent to the wound. The changes in anatomy express the functional need of trees to gain protection and support at the expense of water transport. Xylem hydraulic efficiency was restored in one year, while protection and support lasted over several years.