Bird Poop Trees: Why NYC Must Clean The Washington Square Park Arch

WEST VILLAGE, NY — A tree grows in bird poop. Well, it can, but it shouldn't.

Specialists from the Parks Department Art and Antiquities team gave the historic Washington Arch its annual spritz and shine this week, and shared with Patch how they keep the famous monument gleaming.

A key component of the battle, according Parks Art and Antiquities team director Johnathan Kuhn, is bird poop.

"Bird poop containing seeds occasionally embeds itself in the masonry joints, causing tree growth," Kuhn said.

Every year, the Antiquities team — responsible for cleaning and maintaining the hundreds of monuments throughout the city — inspects, repairs and cleans the 73-foot-tall icon over a multi-day maintanence phase.

The Washington Arch was completed in 1895 to commemorate the 100th anniversary of George Washington's inauguration and suffered years of damage from the bygone era when pollution from traffic under the monument and acid rain from coal-fired furnaces left the arch damaged, according to the Parks website, forcing the city to fence it off for many years due to structural concerns.

On Tuesday, a team took to a boom lift, armed with gentle soap, soft brushes and pressurized hoses, to clean the arch from top to bottom, careful not to damage the soft marble.

The team also cleans the coffered ceiling of the arched understory, a third of which has needed to be replaced over time, said Kuhn.

The team also found some ancient messages when the arch underwent its restoration nearly 20 years ago.

"We had to remove layers of 'parge coat' concrete washes applied for decades to hide graffiti," Kuhn said, "and found graffiti underneath dating to the Cuban Missile crisis of 1962."

But it's not just cleaning. The team also inspects the structural masonry, filling in any gaps with new mortar and making sure water no longer leaks into the monument's innards as it once did, Kuhn said.

"Thankfully coal burning furnaces are largely a thing of the past," Kuhn said, "though damage from acid rain remains considerable."