James Mitchell, a tree worker for the National Park Service, waters the roots of a fallen mulberry tree on the grounds of the Washington Monument. (Astrid Riecken/For The Washington Post)

One day around 1890, the seed of a white mulberry tree, perhaps borne from the droppings of a passing bird, fell on the grounds of the newly dedicated Washington Monument.

It germinated, grew and sank thick roots into the earth. An unlovely tree, it became the abode of bugs, bats and lichens. Tattered kites caught in its branches. And 129 years of history unfolded beneath its boughs.

Over the years, it bent with age. Its roots were exposed by runoff, trampled by human feet and compromised. On Sunday afternoon, battered by wind and rain, its main buttress root snapped and the tree fell.

The National Park Service is now trying to figure out a way to save it, saying the 55-foot former vagrant is a witness to history, and perhaps the only naturally occurring vegetation on the site.

“The weed turned into an asset,” Jason Gillis, a Park Service arborist, said Tuesday.

He said experts are trying to find a way to prop up the tree off the ground and prune it so it survives.

It would still be a fixture on the landscape, although more horizontal than vertical.

A mulberry is often a “volunteer” tree, Gillis said Tuesday as he stood near the fallen tree.

“It sprouts up in places where you don’t want it,” he said. “A lot of people spend a lot of time trying to get rid of them. . . . They can take over a landscape.”

He added: “Here, it was probably a volunteer because there’s no examples of this happening anywhere else. That would also make it the only natural growing tree here that wasn’t somehow man-managed or planted.”

The tree appears, pretty well grown, in an aerial photograph from 1919, and Gillis theorizes that it was “preestablished in the landscape” by then and may date to around 1890.

The tree was probably not on the grounds before 1887-88, when the final grading around the base of the Washington Monument was done, according to a Park Service study.

“If the 1890s theory is correct, that would mean that this tree is . . . what we call a witness tree [and] would have witnessed or been present for any important event in this area in the 20th century” and beyond, Gillis said.

That would include the Rev. Martin Luther King Jr.’s “I Have a Dream” speech in 1963, Vietnam War protests, Fourth of July celebrations, presidential inaugurations, kite festivals, music concerts, kickball and Frisbee events, and at least one earthquake.

Because it’s the only big tree around, it has appeared in many photographs with the Washington Monument in the background, Gillis said.

“Our goal is to try to preserve it in the landscape without reducing it,” he said. “It would stay in the same position. [We] basically just want to try to do a partial raise, give it artificial support with a custom prop, do a little bit of form pruning, then reestablish this root zone.”

The tree rested on its side Tuesday, its exposed roots covered with cloth to keep them from drying out. The tree bark was moist and the grounds were still saturated with water.

A Park Service worker hosed the roots down to keep them wet. The snapped main buttress root, which was about the width of a fire hose, could be seen in the mud.

Beside it stood another, smaller, white mulberry tree, also bent with exposed roots, and also possibly endangered.

Gillis said there once was a cluster of four mulberries on the spot, all probably part of “one conjoined root system.” The two other trees are gone. Park Service officials said they believe they fell within the past three years, because they were present in photographs taken in January 2016.

The fallen tree still has viable “feeder” roots in the ground, and mulberries are known to be hardy and able to survive even after they have fallen. They “can handle pretty much anything we can throw” at them, Gillis said.

“The mulberry lends itself to some abuse, and keeps on kicking,” he said.

He said he hopes to have a plan to preserve the tree within a few days.