A pair of century-old elm trees will be felled as they are riddled with decay.
The grand trees in Preston Park have a severe case of decay in their lower trunks, caused by a common fungus.
Brighton and Hove City Council officials found the decay when they inspected the trees, which are close to the tennis court and bowling green.
Town hall bosses have confirmed the trees’ advanced state of decay is untreatable and they will be felled “within the month”.
Sue Sheppherd, of the Friends of Preston Park, said the trees were probably more than 120 years old.
She said: “It’s very sad news because they are nearing the end of their life and they’re great big elms.
“Like people, they are prone to disease as they get older and that’s what’s happened here.
“I know the council has been carefully monitoring them on a regular basis, including doing ultrasound tests to see what’s been going on inside them. But these two have become rotten on the inside.
“From a health and safety point of view, we don’t want to wait for another big gale where they come down on the road, so they decided to fell them.”
The two trees have been confirmed as Wheatley elms, known in Latin as Ulmus Minor Sarniensis, and will be replaced with two replica species grown in London’s Hyde Park.
But despite the loss Brighton and Hove still boasts one of the biggest elm collections in the country with around 19,000 trees – including more than 100 in Preston Park.
David Alderton, of the Preston Park and Fiveways Local Action Team of residents, said: “It’s a shame because the trees are a part of the historic fabric of the park.
“But the way Dutch elm disease was contained in Brighton and Hove, it means we have a unique population of elm trees, so any loss is worrying.
“Trees have a finite life span and problems do arise, unfortunately.”
A spokesman from Brighton and Hove City Council said: “Tests show the lower trunks of the trees are weak and in an unsafe condition.
“There is no treatment for this level of decay so the trees will be removed within the month.
“We are always sad to lose any mature tree. Removal will only be carried out when there is no alternative option.
“We monitor and care for the trees in our city, taking every effort to preserve their beauty for many years to come.”