It was one of the first trees planted on the Otago Peninsula site nearly 150 years ago by the castle's first owner, businessman and politician William Larnach.
The tree, a Cedrus atlantica, sited just north of the castle, was hit by ‘‘exceptionally strong winds’’ in mid-April and could not be salvaged.
It was planned to plant a replacement tree during the castle's 150th anniversary celebrations next year.
The loss of the tree has added a further twist to one of the toughest months for the owners of Larnach Castle in the past 50 years.
The castle and grounds have been closed to visitors throughout the coronavirus lockdown.
Larnach Castle Ltd executive director Norcombe Barker and owner Margaret Barker were saddened by the recent loss of the huge tree.
The company's night manager Peter Sinclair found that the tree had been heavily damaged by high winds last month, during the Level 4 lockdown, the Barkers said.
It was only under the more recent Level 3 of the lockdown that the castle owners and the garden staff could assess the damage properly.
It had been decided that trying to save the tree would only put the safety of future visitors in jeopardy.
It has bought joy to many thousands of visitors, not only because it was an exceptionally grand tree, but it has also been the home to the Oamaru stone Cheshire cat, which used to grin down from its elevated position.
The cat was fortunately still in one piece, and a new position would be found for him to "look imperiously down on future visitors", the owners said.
About 30m tall, the tree was located about 30m north of the castle.
The tree was an estimated 149 years old, and was one of the first trees planted by Larnach (1833-1898), the castle's first owner, in 1871.
As part of the castle’s 150th celebrations next year, a replacement tree will be planted, in the hope that it survives another 150 years.
