Historical ages are based on some sort of historic reference to the tree. Hartesveldt from Ambassador of Sri Lanka in the USA, December 15, 1972).Old List contains only a single historical age, that for a Ficus religiosa at a Buddhist Temple in Anuradhapura, Sri Lanka. An individual tree may have up to two entries in the database.For a crossdated age, there should be no question of the age of the portion of the tree sampled, except in any portion of the ring series not confidently crossdated with either other trees at the same site or other sites in the area.
In addition to the original , Neil Pederson at Harvard Forest maintains a separate Eastern Old List focused on old trees growing in the eastern US.
However, radiocarbon ages of trees are considered if the date came from a piece of wood that can unequivocally be associated with the individual tree itself. (2007) used radiocarbon dating on pieces of what may be the largest known baobab (Adansonia digitata) to determine that the tree was at least 1250± 50 years old when it recently died.
This is now the oldest confirmed age of an angiosperm tree, at least twice as old as the second oldest confirmed age for an angiosperm species (although note also the addition of two oaks reported in Jones 1959 that are 866 and 930 years, sent to me by Alexei Rivera; however, we cannot find the original references and these presumably ring-counted ages cannot be confirmed).
The tree is still alive, and the age given below, 5062 years, is its age as of the growing season of 2012.
Crossdated ages are derived through recognized dendrochronological procedures (e.g., Stokes and Smiley 1968; Swetnam, Thompson, and Sutherland 1985; Schweingruber 1987; Speer 2010).