Ten per cent of the tree's canopy was removed in 2018 to help improve its lifespan, with a further reduction in height of 15-20m set to take place between November 12 and 13, weather permitting.
Hastings councillor and Frimley resident Kevin Watkins said while it was sad, the tree was considered too much of a safety risk to not take any action.
"This balances the need to protect the community as well as preserve this tree which is a highly regarded, important landmark for both Frimley Park and the country as recognised with its listing as a notable tree on the New Zealand Tree Register," he said.
Despite the reduction in height, the tree will still hold the title of the largest girth of any tree in Hastings' public parks and reserves (10.17m).
The work will require two cranes to be on-site to safely reduce the tree's canopy. The current fence that surrounds it may also be extended to prevent people from endangering themselves by getting too close.
Regular monitoring of the tree will include checking its uprightness, general health and updates on the cracks in the trunk, as well as a specialist arborist will conduct a full tree inspection each year.
It's understood the tree was planted on the original homestead of the Williams family grounds, which now form part of Frimley Park.
The species was believed to have come from France in the 1770s, derived from cuttings of a female American cottonwood.
