"THE Seven Pines" at Brown Hill Creek have been recognised for their historical and botanical significance.
The trees were added to the National Trust of SA's Register of Significant Trees in August following a submission by horticulturalist Charlie Buttigieg in May.
Mr Buttigieg said they were among the largest of their species in the world.
"I was astounded when I saw them," Mr Buttigieg said.
"I knew what I was looking at."
The pines, of which four living, healthy specimens remain, were planted in 1891 and are on average 30m tall with a 30m canopy spread.
The largest tree's girth is just under 7m.
Mr Buttigieg said he believed the trees represented a genetic strain of stone pines with particularly vigorous growth.
But he said the most exciting thing was their link to George Prince, who donated the seedlings to the City of Mitcham.
Prince was a successful pioneer and a major contributor to Adelaide's horticultural development, in particular with regard to roses, fruit and vegetables.
"These specimens have the most well documented genetic lineage of stone pines in the whole of Australia and can be authentically traced back to George Prince's garden at Mitcham," Mr Buttigieg said.
He said there was clear evidence the donated seedlings came from a mother tree in Prince's garden, which was planted shortly after he arrived in Australia in 1849.
He said documents and photographs indicated the mother tree was exceptional.
"We believe it was the largest specimen of stone pine in the history of Australia."
Mr Buttigieg said he hoped to continue his research of "The Seven Pines" with the aim of tracing the trees' lineage back to the mediterranean basin, where stone pines are native.
Mitcham Mayor Michael Picton said having the trees added to the register ensured "a permanent record of the role played by trees in our history, and which contribute to our developing culture."
Originally published as Brownhill Creek trees get National Trust nod