The female guide's convertible car was parked outside Olveston, in Cobden St, when the large beech tree, which was growing in the home's grounds, fell on the car without warning about 2pm.
The tree crushed the car, writing it off.
The woman could not be reached yesterday, but Olveston manager Grant Barron said she was giving a tour at the time the tree crushed her car and had to finish the tour despite knowing the fate of her vehicle.
Mr Barron said the tree had not been touched for years as it was one of several on the property protected by the Dunedin City Council.
Council Parks and Reserves team leader Martin Thompson said the tree was one of 1200 "significant" trees listed with the council.
The listing meant if the property owner, who must still maintain the trees, wanted to do anything with them, resource consent was needed if there was a wish to cut the tree down, or permission from the council needed for other work.
Certain trees were considered significant to the city because of their condition, their impact on the landscape and/or their age.
If property owners noticed any problems with the trees, they could contact the council for advice, he said.
A Fulton Hogan contractor at the site said it appeared the tree's root system had given way.
The tree was to be cleared by contractors last night.
