But is the National Arboretum Canberra, the $70 million tree collection created as a symbol of healing after the city was devastated by bushfires in 2003, a tourism success, a botanical failure, or both?

The venue had 564,000 visitors in 2016-17 and more than 400,000 in the current financial year so far, putting it up there with the city's main attractions.

The visitor centre, with its cafe and spectacular views, is inundated with visitors on weekends and holidays, the quirky, $1 million playground is a hit, and the Margaret Whitlam Pavilion, overlooking the sweeping site, is a popular venue for weddings and funerals.

“Too many visitors is a great problem,” executive manager Scott Saddler said.

“[The original planners] expected one million in five years. I've had to rip up policies and procedures, and put a 10-year master plan in place.”

But when it comes to the trees themselves, the picture hasn’t always been so verdant.

In 2016, just three years after its official opening, a major review of the arboretum’s planning and management revealed that than 1000 trees had died, with another 1800 in poor condition.

Eighteen months on, Mr Saddler says, the arboretum is thriving, and the number of dead or ailing trees is now in the low hundreds - less than one per cent of the entire site of 44,000 trees.

“I'm the type of manager who needs to find, whether they're old or new, all the different techniques to make the forests grow to the best of their capabilities,” he told Fairfax Media.

“There's probably five forests that have always struggled... because of the species and the climate. But I'm not a ‘give up’ manager, so we're now trying to use different techniques.”

These include the recently installed $4 million state-of-the-art watering system, that now pumps bore water to every individual tree from the site, all monitored on Mr Saddler's mobile phone.

Another technique he’s been trialling, with great success, is old-school gelignite blasting of tree-planting holes, as practiced in the old days by Canberra’s founding horticulturalist Charles Weston.

He and his team adopted this technique following advice from local veteran forester Peter Marshall, who has been one of the arboretum’s strongest critics.

But while he has been willing to advise Mr Saddler and his team, Mr Marshall stands by his comments from 2016, when he declared the project a failure from the get-go.

He maintained the decision to plant a monoculture arboretum - large blocks of single species, rather than scatterings of different types of trees - was detrimental to the trees’ survival.

That, combined with the decisions on plantings made in the arboretum’s early stages, and the harsh, arid, windy environment of the site, meant the project was largely doomed, he said.

“I admire what they’re doing up there, and their commitment to the arboretum, but my feelings about its long-term position are the same,” he said.

He reiterated that his criticism was aimed not at Mr Saddler and his management team, but at those who conceived the original design and selected the species for planting.

“They’ve basically created a situation where the lifespan of the trees is compromised and the end is death,” he said.

“The whole arboretum has been overplanted by a factor of about 10.”

He maintained that even a top-notch watering system wouldn’t compensate for the dry, arid winds.

“It’s truly astonishing that they were allowed to get away with it, and frankly, the ACT government should ask for its money back,” he said.

Former chief minister Jon Stanhope, who conceived of the arboretum in the weeks following the 2003 bushfires, and withstood significant political and personal criticism as he stood his ground in the ensuing years, has mixed feelings about the plantings, although not about the results.

Now the arboretum’s patron, he said he was “generally very happy” with the way the arboretum was being run, and with its current state.

But he said if he had his time over, he would have been more critical of the design and planting process.

“I think perhaps, rather than just accepting unquestioningly the advice of the tree panel on tree species, I would have been a little bit more demanding about the selection of trees that weren't going to struggle to survive in our conditions,” he said.

“For instance, there are some trees there that are a tad sensitive to cold and frost, and if somebody had told me at the time, I would have said, ‘For goodness sake, don't plant it. Find something that's not going to curl up in a -5 frost’.”