Environmental campaigners said they are devastated that one of four trees which was saved from the chop has been felled after it was found to be diseased.
Newark and Sherwood District Council had planned to cut down four mature trees to make way for a car park extension in London Road.
But a campaign by local people against the plan gained national attention and the council reversed the decision at the eleventh hour in November 2021.
But one of the four trees, an acacia, has decay in the main stem and was felled on March 23 “for safety reasons”.
Protect Newark’s Green Spaces say they are having a bench made from the wood for the Library Garden, and may use some of the wood for bird boxes and bug hotel kits.
They are also hoping to make the tree stump into a seat.
Newark and Sherwood District Council has closed off the area this week due to “essential tree maintenance work to protect, sustain and enhance the site for the future”.
The authority said it has contracted a tree surgeon and has met with representatives from the campaign group who are comfortable with the work taking place on site.
Work will also be carried out on five other trees in the garden.
The original plan to fell the trees followed a legally binding agreement Newark and Sherwood District Council signed with Datch Properties Limited in 2019, which committed the council to building the car park.
The council said it reversed the decision after receiving a last minute offer from the developer in November.
Despite the sad news, campaigners said there are “many exciting changes afoot” for the library garden and are “bubbling over with ideas and have many exciting plans”.
They said they are planning to buy wildflower plants for the garden and hope to have a garden designer on the site soon.
Protect Newark’s Green Spaces said: “It goes without saying that we are all devastated to lose the false acacia. As a campaign group, we fought so hard to save all the trees in the Library Garden and to lose one is an undeniable blow. However, please be assured that the garden and the other trees are safe and that we are determined to honour the false acacia’s legacy in a number of ways.
“We hope everyone understands that the false acacia will still be very much part of the garden that we saved and that it will continue to be enjoyed by our community, which is all any of us ever wanted for this wonderful green space.”