A lone cladocalyx down here in Melbourne can be that size quite easily by about 80 years. Could be 100.... but I doubt any older.
Does the age of the building or other site history give any clues?
What suburb?
We are taking down the remains of a severely storm battered one tommorow at a National Trust Property. One of a large stand planted in the late 1920's.
Oh, going by the pic, I think your Diameter at Breast Height measurement must be circumference to give 4.9m
DBH will be approx 150cm
