Nigel Ryan, a trustee of Grove Garden, said the tree was felled in February after it was seen ‘swaying dangerously’ following Storm Eunice.
He said it landed in Grove Garden, damaging the wall, after an emergency decision to fell it was made by Mid Sussex MP Mims Davies and Mid Sussex District Council leader Jonathan Ash Edwards.
“I don't think they could have left the vicinity with the tree in the state it was in,” said Nigel.
But he said the tree is now preventing the garden team from doing anything.
“It’s a hefty beast, so it’s still in the way,” said Nigel.
“We were due to open the garden up to the public at the beginning of June and start having fundraising events,” he added.
Nigel said the team managed to chop some of the tree and trim branches but cannot move the remains without a professional.
“We actually got some quotes from a tree surgeon, I think it was about £2,500,” he said.
Nigel feels Grove Garden should not be responsible for removing the tree because they did not make the decision to fell it.
He said he would like Mims Davies and Jonathan Ash-Edwards to resolve the situation, possibly through Mid Sussex District Council.
Ms Davies said: “The right and urgent decision, due to the danger to life situation local residents found themselves in, was made to fell this beautiful but very dangerously unstable tree when storms raged earlier this year.
“Unfortunately the clear-up process has been somewhat delayed while suitable funds are sought to cover the costs and impact.
“The insurer of the property on whose land the tree stood, and which could have been significantly damaged with a high potential of personal injury had it been allowed to fall that way, have refused to pay on the basis that their client (who was unavailable at the time of this emergency) did not engage the tree surgeon.”
Ms Davies said a ‘suggested alternative’ to funding the repairs and removal had been shared with Grove Garden Trust, which could provide a workable solution.
The district council has been approached for comment.