26/03/2016 4:16 PM AEDT | Updated 29/12/2016 7:56 AM AEDT

The Herbarium: A Hidden Secret In Sydney's Royal Botanic Gardens

Sydney's Royal Botanic Gardens are an oasis occupying 30 hectares of one of the harbour city's most spectacular positions.

Established in 1816, the Gardens are the oldest scientific institution in Australia and are home to a collection of native and exotic plants.

What most people probably don't know is that the Gardens are home to the Herbarium, one of Australia's biggest reference collections that houses over 1.2 million plant specimens, which are used to study the ecology, evolution and classification of plants.

However, according to Dr Brett Summerell, Director of Science and Conservation at the Gardens, even though this seems like a lot, there are still many plant species in Australia that are yet to be discovered, but it's anyone's guess as to how long this could take.

"Our best guess estimate at this point in time is that we think we've collected about 85 percent of the higher we think there's about 15 percent left," he told The Huffington Post Australia.

"Once you get into some of the less well-documented groups of plants like mosses, and liverworts -- and the things that I work on, the fungi -- we think that there may well be anything as many as 50 percent of those still undescribed.

"And the fungi that I work on, we think we might have 12-15 percent of them discovered and documented, so there's still another 85-90 percent of those still out there to be discovered and documented."

The Herbarium has a rich history with some of its pressings of plant specimens first collected by Joseph Banks and Daniel Solander -- two botanists that were on Captain James Cook's first voyage to the Pacific Ocean in 1770.

Making the pressings is a long and arduous task, beginning in the field when a cutting is taken and is then pressed between newspaper and bits of cardboard on the journey back to the Herbarium.

The specimen then goes through a drying process so that it doesn't become mouldy or covered in growth, before being placed in a freezer for seven days to eradicate any insects that could potentially infest and destroy it.

Once dried and frozen, a team of volunteer plant specimen mounters arrange it out on an archival sheet of mounting paper and, using dental floss, tie it to the sheet with a label clearly outlining the details of the plant, who it was collected by, when it was collected and also information about the locality and ecology of where it is from.

"One of the great things about working in an organisation that is this old -- 200 years old this year -- is that you work with a collection that's seen the whole span of European human endeavour in this country," Summerell said.

"So it is a real privilege to be able to work with collections like this, to document why plants have existed and where they've existed, how they've evolved and how they're responding to changes in our environment."

This story was originally published on 26/03/2016