At least two forests at the National Arboretum are struggling on the site and tough decisions on their future will soon need to be made, the attraction's new patron Jon Stanhope says.
The former chief minister, credited as the arboretum's founding father, was announced as its first patron on Friday.
While the voluntary position as a "roving ambassador" for the 250-hectare site will be non-operational, Mr Stanhope said he was looking forward to being involved in discussions with TAMS staff in control of the site.
"There are some forests within the arboretum that haven't performed," he said.
"It's an interesting stage in the future of the arboretum. It's gone through its infancy and its now growing up and there are additional and new challenges."
Mr Stanhope said he hadn't been advised of detailed investigations into the struggling forests, but from his own observations at least two "did not like the site or conditions", including the forest of rare Buchan blue wattles, a Victorian native.
"It was to some extent an experiment when it was planted," he said.
"There was a bit of a wing and prayer around the decision."
According to the arboretum's website, the blue wattle forest, planted in 2008, was now incomplete as some trees had died due to having been waterlogged.
Mr Stanhope said planting the remaining 10 forests to complete the project was a top priority, but he didn't envisage any major changes to the attraction, which had a record more than half a million visitors in 2015.
"I did always expect it would be popular, there were times when I worried, but I didn't expect visitation would be as high at this stage of its development as it is," he said.
Mr Stanhope previously expressed a preference for a job at his other legacy project, the Alexander Maconochie Centre, over the arboretum, saying there were "far more important things than a pretty forest" when he returned to Canberra in 2014.
But on Friday he said he visited the beloved arboretum at least once a week and it was the No. 1 subject members of the public approached him about in the street.
"It's always positive and people are so enthusiastic in their support and love of the arboretum and the extent in which they use it," he said.
Territory and Municipal Services Minister Shane Rattenbury said strong infrastructure decisions would soon be made to implement the masterplan, including the future of the struggling forests.
"By their nature arboreta have an experimental component to them," he said.
"The question will be 'do we seek to attempt the same forest again?' or do we accept that the forest isn't right for this or the Canberra landscape and think about a new forest."
Nominations for board members on the arboretum's newly-created foundation established to help drum up financial support from corporate sponsors and private benefactors, after an overhaul of the management last year, close on Friday, February 12.
Mr Stanhope said he'd chosen not to be a member of the foundation because of pressure from his other work and did not expect to have a formal relationship with the group.
Mr Rattenbury said the patron role had a broader remit as an ambassador for the arboretum, promoting it and inspiring the community.
He saw the foundation focusing fundraising efforts on "more visible changes" whereas "less glamorous" infrastructure work like irrigation would be paid for by the government.