Workers clean up an area on the grounds of the Washington Monument on Wednesday. (Ricky Carioti/The Washington Post)

Ah, spring in Washington. Cherry blossoms, daffodils. The smell of flowers, cut grass and, on the grounds of the Washington Monument this week, cow poop?

A rank odor that visitors likened to cow deposits was borne on the breeze this week from a large mud flat left behind from Saturday’s Global Citizen 2015 Earth Day rally, just northeast of the Monument.

“The mud flat was caused by a combination of overuse and rain at inopportune times,” National Park Service spokesman Mike Litterst said in an e-mail Wednesday.

“With the turf restoration going on along the National Mall, events that might normally take place there are being moved to the Washington Monument grounds, creating almost constant use this time of year,” he said.

Visitors to the Mall complained of a smell coming from the muddy area. (Ricky Carioti/The Washington Post)

“Saturday’s Earth Day event was preceded by the Cherry Blossom 10 Miler and Make-A-Wish Foundation’s Walk for Wishes on April 12,” he said.

Flooring was used to protect the grass, he said, “but if we get substantial rain (as we did both during setup and strike of the Earth Day event) water seeps under the flooring and creates the muddy conditions.”

And unlike the recently restored turf panels on the east end of the Mall, the grass on the Washington Monument grounds already was in poor condition.

The odor was especially strong Tuesday, when passersby were seen covering their noses with scarves, but lingered into Wednesday.

Litterst said it “came from mud and other organic materials that were already on site when the flooring was put down.”

“The rain that falls and seeps under the flooring creates a perfect ecosystem of decaying organic material, so once the flooring was removed, the odor of rotting organic materials and mud was unleashed,” he said.

“Smells like cow poop,” a youngster from a Fairfax County public school said Wednesday as she and her classmates held their noses near 15th Street and Constitution Avenue NW.

An adult with the children declined to further identify the group but said they would head away from the smell.

“Clearly, this is a problem,” she said. “We were going to walk up and take pictures (of the Monument), but I think we’re going to stay here and then go see the White House.”

Nearby, Diane Diehl, 43, of Wilbraham, Mass., laughed as her sons, Jeremy, 10, and Paul, 7, held their noses.

“Smells like cow manure,” she said. “It’s not exactly pleasant.” She believed the area was being fertilized. “We hope that’s what it is, too. And not anything else.”

Asked about the smell, Jeremy said, “It’s gross.”