Hundreds of New Yorkers stopped by Union Square on Sunday to pick up daffodil bulbs and wildflower seeds as part of a long-running citywide planting effort.

The event was part of the Daffodil Project, an initiative launched after Sept. 11, 2001, as a symbol of remembrance and renewal by the nonprofit New Yorkers for Parks. It was the fourth of seven events scheduled across the five boroughs over two weeks.

Every year, tens of thousands of people pick up free bulbs and plant them in street tree pits or community gardens. The flowers bloom in the spring.

The project began when a Dutch bulb farmer donated 1 million daffodil bulbs to New York City in the aftermath of the 2001 terrorist attacks. New Yorkers for Parks took on the initiative, and it has since become a key part of its advocacy platform.

“People getting their hands dirty and doing work to improve their communities is really just a powerful message,” said Adam Ganser, the group’s executive director. “These daffodil bulbs help people do that.”

The group distributes between 500,000 and 1 million bulbs annually.

But the campaign goes beyond flowers. It’s also a vehicle for pushing City Hall to increase funding for the city’s 30,000 acres of parkland through its “1% for Parks” campaign, a call to dedicate $1 billion, or 1% of the city’s $116 billion budget, to parks.

“Those parks, if they were invested in appropriately, can do so much more to make the city healthier — to reduce water during times of rain and flooding, to decrease the temperature in neighborhoods that are suffering from higher temperatures because of a lot of concrete,” Ganser said.

According to New Yorkers for Parks, most major cities spend between 2% and 5%.

The next Daffodil Project event is Saturday at A. Philip Randolph Square in Harlem. Bulbs will also be handed out at Willowbrook Park on Sunday, Sept. 21, and at the Rise Center in Far Rockaway on Friday, Sept. 27.