Momentum is gathering for the 44-year-old research institute and its layers of seeds, living specimens and growing events calendar to break out of its borders.

Mr Byron says a consortium of leading architects preparing a 20-year master plan is proposing a pedestrian bridge over the garden's Black Mountain Drive boundary into 40 hectares of empty bushland, where new features will complement the institution's popular tourist attractions.

Mr Byron said architects Tonkin Zulaikha Greer and landscape architects Taylor Cullity Lethlean wanted to put their ideas into a public forum for feedback.

"What a lot of people don't know, we have another 40 hectares of bushland across from Black Mountain Drive, it is called our southern annex," Mr Byron said.

"We have also incorporated some ideas for there as well in the future, it may be a large nature play area. Well down the track, there is potential for eco-tourism. There could be all sorts of adventure activities, ropes, courses, interactive-type facilities for children."

A more formal pedestrian path to the National Arboretum is also planned.

The 40-hectare gardens' rainforest gully, vast numbers of mature trees and shrubs and prolific water dragons and birdlife draw international visitors as well as Australians, and planners want to give them a clearer overview on arrival.

Mr Byron said the 1960s office was built with a floating roof, and architects suggested turning this into an an open pavilion and links between a new visitors' centre and new cafe.

All maintenance depots will go to the back of the site, opening up a large area which can be developed into an amphitheatre and events.

"The feedback we've had is the eucalypt lawn is a beautiful space for summer concerts and so forth, but it is a bit of a walk up the hill, and if we could have an events space closer to the car park and cafe and visitors' centre, it would be more attractive," Mr Byron said.

The master plan, which provides for a new seed bank, will dovetail into the CSIRO and ANU's new $200 million scientific hub to research food security and sustainability.

"We want to take a precinct approach and not just plan in isolation," Mr Byron said. "Part of that precinct approach is how we can link up with the [National] Arboretum, as far as a walking track, to get more people connecting between the two sites, and looking at how we can better connect with the lake [Burley Griffin]," Mr Byron said.

"We are not changing things just for the sake of it, we are looking at re-purposing the buildings as much as possible. The current visitors' centre will be used for staff.

"We would like to re-use some of the classic architecture from the 1960s and incorporate into design and make this as cost-effective as possible."

Work will be funded from within the garden's capital expenditure budget and fund-raising, including ongoing invitation for private sector partners, provided this did not conflict with the gardens' core scientific values.