The historic estate’s extensive garden has been added to by each generation of the MacDonald family since settling on the property in 1853.
The lily — or cardiocrinum giganteum — is believed to have been brought to South Canterbury in the early 1900s by the Aclands of Mt Peel.
Geraldine Historical Museum secretary Margaret Chapman said legend had it, when the Mt Peel glasshouse broke after snow, the plants escaped and flowered.
Mrs Chapman said "It is more likely that after seven years of building strength, these tree-like lilies burst into flower."
The lilies were introduced to Orari Estate in about 1914, where they had thrived ever since.
She said those at the museum were thankful to the Morten family, who own OrariEstate, for allowing the public a glimpse of their gardens.
The event was a fundraiser for the museum. Gate entry is $10 per adult and children are free.
"Come along and enjoy a ramble through a large country garden and view these magnificent plants in full bloom and enjoy their exquisite perfume."
Mrs Chapman said the lilies were a real treasure in the garden over the Christmas period when the 2-4 metre stems carry huge scented white trumpet flowers.
"Bring a picnic and enjoy a day of relaxation, by the pond or under the trees listening to the bird life and enjoying the peace and serenity of a large country garden."
Held on December 10, the garden would be open from 10am-4pm.
Orari Estate is on State Highway 1, just north of Orari, and will be signposted from both Orari and Rangitata.