One of the most interesting Nature Reserves is the complex of nearly a thousand oak-trees over 500 years old in Rogalin, Wielkopolska. A few years ago alarming condition of the trees necessitated an expertise and working out of a special preserving treatment. The methods used throughout those years have brought satisfactory results and may be recommended for further use. Besides routine statics improving - interventions and desinfections, several agro-technical measures have been taken. One of the most important was intensifying the impairment overgroving process through introducing some stimulating means into the tissue forming places.