Abstract: The present paper aims to model the potential for conservation of some very large specimens of either indigenous or human introduced tree species located within the Continental and Steppic Biogeographical Regions of Romania, areas characterized by considerable natural diversity. Centuries of human intervention have resulted in the major replacement of the natural vegetation with semi natural forests in the highlands, pastures and permanent crops at the hills and arable land in the lower areas. The once pristine landscapes present numerous remains in the form of old trees, while other exotic introduced species are common. In order to assess their conservation potential, we applied an encyclopedically approach centered on numerous field observations, measurements, scientific literature research, historical maps analyses and discussions with locals. The results certify the existence of different species characterized by a medium and high potential for conservation. Some of them are the subject of numerous researches and possess favorable conservation status while many are poorly or virtually unstudied and not protected. Such findings are usable in complex domains, mainly biodiversity conservation, durable ecosystem management and ecotourism.