A site tree should belong to the dominant or co-dominant overstory class.
[1] The total height of the tree and age measured at Diameter at breast height of a sample of site trees will be used to determine a site index, which will show how tall trees of different species can grow on that site in a set amount of time.
Sometimes several years are added to the breast-height age to account for time grown below 4.5 feet (1.4 m).
Finding a site tree is more difficult in uneven-aged, mixed species, stands.
Each site tree is assumed to have been a dominant or co-dominant individual its entire life.