Birdwatching, pond dipping for bugs, nature craft and yoga were among activities on offer as part of the garden's 45th Anniversary Community Day.

Seven-year old Pollyanna Butterworth, of Ngunnawal, was among nature lovers exploring the gardens from behind a set of binoculars.

Mother Nicole Butterworth said her daughter's favourite bird was the king parrot.

The family, including siblings Violet, 10, Weylan, 7, and Lucinda, 4 also potted a daisy to take home, cracked open rocks to find fossils and enjoyed a picnic on the lawns.

"We went as a family to do the bird walk. It was a big family day out," Ms Butterworth said.

"The kids really enjoyed the bird-spotting. We also saw a lot of lizards."

Ms Butterworth said the family visited the gardens at least once a year but spring was the most stunning time to walk its tracks.

"October is the best month to go. It was in full flower," she said.

Event co-ordinator Helen McHugh said a steady crowd of people enjoyed the garden's "spectacular" blooming buds, the largest living collection of native Australian flora, throughout Sunday.

But it was also an opportunity to engage young nature lovers with science and scientific processes.

"It's just the right weather to be going for walks through the gardens," she said.

"You can smell the boronia – all those pretty scents.

"Lots of happy people have been collecting bugs and doing yoga."

The gardens were officially opened in October 1970 by then-prime minister John Gorton.

Ms McHugh said the anniversary celebrations included activities for the young, the young at heart and adults.

She said the day's highlights included the opportunity to create a miniature "bee hotel" to attract native bees into the garden, and collecting spiders to view under a microscope.