Revitalization experiments on an old oak


  • Alfred Becker
  • Arnold Irle
  • Jan I. Lelley


A common oak (Quercus robur L.) named “Bear-Oak” in South Westphalia, aged about 650, taller than 30 m and with a diameter of over 1.6 m is under preservation order. This tree was seriously ill in summer 1990. Visible causes were a lightning strike and infection with fungal saprophytes. The most obvious symptom was that rotten strong branches broke off from the crown.

The original intention of the natural protection agency in charge was to exempt the tree from the preservation order and to let it “die honourably.” However, revitalization measures such as revitalization of the crown, restoration of lightning wounds, mycorrhization, and fertilization of specifi c sites were performed in September 1993 on the suggestion of the Research Institute for Mushroom Cultivation of the Rhineland Chamber of Agriculture in Krefeld. The outcome of these measures was recorded and monitored in the following years by scheduled recording of vitality parameters (extent of mycorrhization, density of foliage, periodic volume increase) to fi nd out whether the overall health of the oak had improved. Although the development of these parameters at the time of the report demonstrates variation in the productivity/vitality of the tree, it also shows that the functional capacity of the oak has recovered to a normal level.

The vitalization measures can be assessed as successful, and intermediate to long-term survival of the tree appears to be established.