When Peter Olde, a newly returned Vietnam War veteran, was establishing gardens in his Illawong home in the 1970s, a friend suggested growing plants native to Australia was the patriotic thing to do.
"That rather took my fancy," he said as he looked back on how his interest in native flora developed.
"I had never thought about it before, but it seemed that it was like running the flag up for Australia and doing something important for the environment at the same time."
Mr Olde not only embraced the idea, but embarked on a voyage of discovery that led to him becoming a world expert in this field and pre-eminent in knowledge of Grevillea.
His contribution to the knowledge of Australian native flora, made in a totally voluntary capacity, led to him being awarded the medal of the Order of Australia (OAM) in the Queen's Birthday Honours.
Mr Olde joined the Australian Plants Society (APS) Sutherland group in in 1977, quickly becoming president and serving until 1982.
He became leader of APS's Grevillea Study Group in 1980, a position he continues to hold. He was appointed NSW life member in 1998 and received the Australian Plant Medal in 2015.
Mr Olde said his interest in Grevillea was aroused by the ability and power of the genus to attract native birdlife to his garden.
He has since co-written the three volume Grevillea Book and, from 1993, been Honorary Research Associate at the National Herbarium of NSW at the Botanic Gardens.
He has described many new species of Grevillea and collected over 5000 specimens all over Australia. Grevillea oldei was named in his honour
In 2003, he and his wife Margaret established a hobby farm at Oakdale to display native plants to their full potential.
Silky Oakes, as it is called, was a regular participant in the ABC's Open Gardens Australia program, which ended in 2015.
The park-like garden, which is filled with hundreds of native plants, including many species and cultivars of Grevillea, can still be viewed by appointment.
"Our aim was to create a garden that would display the best of Australia's native plants in the most beautiful manner possible," Mr Olde said.
"We now have one of the largest collections of Grevillea in Australia."