As a result of the work, Ridgway St, where it connects with Guyton St, is closed to cars and pedestrians.
The arborists are using a combination of climbing and bucket trucks to access and cut down the trees in large sections.
Tree Truck director Brett Stevenson said after counting the rings of one of the cut-down trees he suspected they were about 100 years old, possibly older.
The trees were being brought down as part of the council's planned maintenance schedule, council parks officer Claire Lilley said.
"The majority of these pine trees have long weighty limbs and branches.
"This poor form means they are at risk of breaking or toppling."
She said the trees had become a local feature in that part of Whanganui.
"While these trees are not listed as protected, we appreciate that they will have provided shade for Cemetery Circuit spectators, and visitors to the cemetery, for many
years," Lilley said.
At the start of December 2021 one of the large cemetery pines snapped from its base, fell and landed on a car parked on Ridgway St.
Lilley said council had to maintain open spaces and keep them safe.
"The council's priority is maintaining our open spaces and keeping them as safe as possible.
"We have an obligation to ensure that we manage risks to public safety from trees that are at risk of falling."
Once the trees were removed, the bank would be replanted with native plant species and planting would be complete by about August, Lilley said.