Common oak is a long-lived deciduous tree species. Full-grown common oaks are 10 to 25 meters high and have thick stems and strong branches. In Finland, these trees flower late in the spring and their fruit, acorns, ripen in the end of September - the time of autumn foliage.

Common oak prefers herb-rich forests but is not particular considering its site demands. It is found in heath forests, on clayey soils and near rock outcrops. The species is common in most parts of Europe and its area of distribution is bordered by southern Fennoscandia in the North and western Russia in the East.

Common oak has previously been an important raw material for shipbuilding and nowadays the wood is utilized mostly as material for furniture and parquet floors. Acorns can be made good use of when making caffeine-free coffee substitute. There are approximately 500 species dependent on common oak and several bird species nest in the holes of branches and stems.

Common oak has an important role in safeguarding biodiversity because it provides a habitat for a diverse group of insect and animal species. Wild common oak forests belong to the habitat types protected by the Finnish Nature Conservation act. Changing their characteristic features is prohibited. However, full protection of common oak forests is not the best option since it should be allowed to remove the spruce trees shading common oaks and lush vegetation. Thus the open and bright environment created by common oak is maintained and survival of common oak dependent species is made possible.