The National Capital Authority says a public park should not be locked up for eight or nine months of the year and has been pushing the ACT government to reduce disruption. It wants a smaller area locked up long-term for direct plantings, with more mobile planter boxes.

Mr Barr said he had taken his concerns about viability directly to the authority's chairman, Terry Weber, and chief executive, Malcolm Snow.

In an interview this week, Mr Snow said the problem was the time taken in set up and deconstruction. While some parts of the park would continue to be made available for longer periods for planting out, the authority wanted other parts closed for just a month before opening. He cited the Enlighten festival's two to three week set-up.

"Why can't we, for parts of Floriade, do the same sorts of things?" he said.

"The issue has all along been the fact that so much of the park for quite a long time, eight or nine months, is actually in our view a construction site," he said. "We are talking about a public park ... So one of our concerns all along is the extent to which the establishment of the event and once it's over, the deconstruction of it, whether or not the timeframe can be reduced."

Mr Snow also raised concerns about damage to trees from heavy vehicles, which compact the soil, resulting in two to three mature trees dying each year, and said the authority would impose an exclusion zone around some trees.

But he stressed it would not do anything that made Floriade impractical or too expensive.

Another problem for the ACT is having to pay parking fees to the National Capital Authority. The bill was $123,000 this year, and the ACT wants to negotiate less, but Mr Snow said the authority was not in a position to offer discounts.

Mr Barr, speaking at hearings into the territory's annual reports last week, said negotiations were continuing to find a "viable footprint" in Commonwealth Park beyond 2016.

There was "no easy alternate site", he said.

"None provide the totality of experience and proximity, transport, accessibility and the like that Commonwealth Park does, so it has been pleasing to hear a reassurance from the National Capital Authority that it is not their intention to boot Floriade out of Commonwealth Park," he said.

He also revealed that the Westside container village is in the mix to host Floriade "fringe-type events", among other sites, including Glebe Park, Garema Place and New Acton beyond 2016.

ACT director of arts and events Adam Stankevicius said the government had an eye to the demographics in choosing a site.

The "large-scale visitors" that visited by bus were an older demographic, including people from aged care homes.

"We need to make sure that we have got a site that is accessible for them," he said. "... On the current site, it is a very accessible site for a wide range of people who have mobility challenges and a range of other issues in terms of accessing the site. So if we do have to find another site, it is not just laying the flowers out and making the bulbs grow; there is a whole range of accessibility issues that we also need to come up with."

Nightfest was another complication "because we cannot just pop up Nightfest somewhere if we are competing with existing traders or we are going to have a whole range of other issues that might impede on the smooth running of that night-time event".

At the moment Floriade was designed so the crowd moved "kind of in a circle", with a number of areas for exiting safely. The National Capital Authority's original suggestion would not have allowed authorities to address those issues, he said.

Mr Barr's spokesman said the 2016 event would see more transportable "drop-in" beds, which were trialled this year, and less disruption in the set-up.

Mr Snow said the authority would sign an interim one-year deal with the ACT for the 2016 festival, then look to sign a longer-term arrangement, five years plus, depending on results in 2016, giving the ACT certainty to plan and invest.