A 200-year-old eucalyptus tree on the banks of the Swan River has been added to Western Australia's State Register of Heritage Places.

The tree, a flooded gum, was one of several in Upper Swan used as boundary markers between settlers' land grants in the Baskerville area in the 1820s.

The area was first visited by James Stirling in 1827, who returned with John Septimus Roe in 1829 to distribute the land grants.

In its Statement of Significance, the State Heritage Office said the tree was a "rare remnant of the early British exploration and survey of the Swan River Valley".

WA State Heritage Office assessment and registration director Penny O'Connor said it was rare for a tree to receive a heritage-listing.

"The state register is primarily for places of cultural heritage significance, not for places of natural heritage significance," she said.

"Any tree that does make it onto the state register has to have that overlay of cultural heritage."

In its assessment the State Heritage Office described the tree as approximately 20-metres high, with termite holes and several missing upper limbs.

But it noted the gum was still "putting forth fresh green branches".

The tree had been "badly burned" by fires in the past, and Dr O'Connor said it was difficult to tell how long it would live.

"Eventually all trees do die so we'll need to acknowledge at some point that, in the future, the tree won't be there anymore," she said.

"We might need to look at other ways of recognising the boundary marker that was there.

"Another tree could possibly be planted in its place, even from the same genetic material."

Dr O'Connor said the State Heritage Office was working with the Department of Parks and Wildlife to help the tree live longer.

"For the moment the tree is still alive, and we're going to get an assessment of the health of the tree and look at whether there's any management strategies we can put in place with them," she said.