NEW YORK — Every Sept. 11, Michael Collarone, a Brooklyn-bred florist who goes by Mikey Flowers, has the same routine. In the hours before 8:46 a.m., the time the first plane struck the World Trade Center 19 years ago, he parks his truck in downtown Manhattan and, bearing buckets of angelic white roses, walks to the site where he once helped scour for victims' remains in the twin towers' smoldering wreckage.

There, the burly 62-year-old meets up with "my guys" from the Port Authority police. This year, he will be wearing a mask for the first time and, for social distancing reasons, the victims' names will be played from recordings on a loudspeaker rather than read aloud from a stage, but little else will change for him. "I'm going to hug my friends," he says. "I'm going to hug my guys."

Collarone’s steadfast devotion to honoring the victims of 9/11 isn’t a once-a-year kind of thing, though. He’s been the de facto volunteer florist to Ground Zero since it was known around the city as the Pile or the Pit. And that didn’t change when the novel coronavirus forced New York to freeze in place in March, and the National September 11 Memorial Museum chained off its eight-acre plaza. A couple of days a week, as he’s done for the past eight years following the memorial’s opening, Collarone or members of his shop would drop off a donation of 50 to 100 white roses.

The flowers are part of what’s known here as “the birthday rose gesture,” given to those who ought to have been celebrating that day, and a reminder that the 2,977 people who were lost on 9/11 once lived vibrant lives.

For months at the memorial, the roaring waterfalls in the footprints of those fallen buildings stopped flowing. Throngs of tourists were replaced with chirping birds and a lone maintenance man mowing the lawn.

And yet, every day, a handful of white roses could be seen poking up from the bronze parapets engraved with the names of the dead.

“It’s about commitment to a cause, to a belief that even when times are tough, we will always remember these people and never forget,” Collarone says of the tradition he was able to keep going with help from the memorial’s security team — many of them former police officers — who place the roses most days, and take pictures and send them to the victims’ families so they know someone was thinking of their loved one on that person’s birthday.

“You know, not everybody’s relative gets to go to the 9/11 memorial,” says Collarone. “That’s what the whole birthday program is. We’re there to stand in for the relatives who couldn’t make it. We always have you.”

On Friday, six names will be adorned with white roses.

Amelia V. Fields, 46, had been working at the Pentagon for only two days when Flight 77 crashed into the imposing military fortress outside Washington.

Ivhan Luis Carpio Bautista, 24, a cook for Windows on the World, was supposed to take the day off but subbed in for a co-worker.

AnnMarie Riccobini, 58, a billings supervisor at a law firm, had just beaten breast cancer.

Michael J. Berkeley, 38, had just founded his own brokerage.

Michael P. LaForte, 39, a broker, never met his third child, born two months after 9/11.

FDNY Lieutenant Vincent Francis Giammona, 40, last spoke to his wife while en route to the burning towers.

Family members often reach out to Collarone or to the memorial’s staff, touched and surprised that the ritual has endured during the pandemic. “It is with tears of gratitude that I write this,” said Jennifer Glick in an email to the memorial. Her brother Jeremy was among those who rushed the hijackers on Flight 93, which crashed into a field in rural Pennsylvania. “With all the insecurity and chaos that we face right now, knowing that our loved ones are remembered gives me great comfort.”

Kerry Irvine, an artist, used to visit the memorial often to think about her sister, Kristy Irvine-Ryan, a 30 year-old equities trader who had been married for just three months when she died. But in March, she told The Washington Post, “It was all chained off, and one of my first thoughts was, ‘Oh, God, her birthday,’ which was May 22nd.” Then she got a photo of her sister’s name decorated with a white rose. “To know they’re taking care of all of them, and giving them the respect they deserve,” she said, “it takes the load off the families a little bit.”

The memorial grounds reopened July 4. The museum will begin allowing visitors inside again this weekend — first, family members only on Friday and then the public on Saturday, with drastically limited capacity.

Collarone didn’t come up with the idea for the birthday flowers; that was a volunteer in the museum. But he’s the one who’s made it happen all these years, carefully selecting roses — he wants them to be a perfect white — from the city’s flower market and cleaning them and nursing them at his shop Flora Tech, in Manhattan’s Tribeca neighborhood. “I’m not looking for the cheapest roses,” he says. “I look for the best.”

When the pandemic forced New York to shut down, halting inbound flights bearing hard-to-get white roses from global suppliers in the Netherlands and South America, Collarone knew instantly “that I had to take care of it,” he says. “I went into an immediate rescue mode for the 9/11 memorial.”

Whereas roses had been coming in on 10 flights a day, there was now one flight a week from Europe. He worked connections (“My Holland guys helped me out.”), paid large markups as freight prices soared, and sent drivers to the airport to pick up loads of roses directly from the source, circumventing wholesalers, because, he says, the city’s flower market, then and now, “is operating on life support.”

His own shop, which used to supply flowers for Madison Square Garden and high-end hotels like the Mandarin Oriental, has hit dire straits. “We’re lucky if we make enough money to keep our electricity on,” Collarone says. He’s had to close all three of his retail flower storefronts, and lay off all of his employees, some of whom had been working with him for 20 to 30 years.

Still, he wouldn’t dream of stopping the birthday-rose ritual, or asking for payment.

He “grew up poor,” he says, in the firemen-and-cops enclave of Dyker Heights, Brooklyn, and worked in a flower shop as a kid before becoming an insurance salesman.

It was a chance meeting with Andy Warhol at the legendary Limelight nightclub, he says, that got him to turn back toward his love of flowers. Warhol commissioned him to decorate his parties, Collarone says, because the art icon was amused by the idea of this insurance guy with a Brooklyn accent who rode his Harley around town and knew everything about roses and hydrangeas.

His shop is near the World Trade Center, and in 1993 he had rushed to the scene when a terrorist drove a yellow Ryder truck filled with fertilizer into the building’s garage and detonated it, killing six and injuring more than 1,000. After that, he got his EMT license and was on site with other rescue crews when both towers collapsed that Tuesday in 2001. He ran into a basement loading dock with about 80 others and was trapped under the rubble before being rescued, he says.

“All the people that I was with had seemed to perish,” he says. He spent the night on a cot in a makeshift medical center at the site, and then kept digging through the debris for months.

Port Authority Police asked him to be in charge of the makeshift memorials that sprung up around the site. He donated wreaths for fallen firemen. On Mother’s Day, his mother came and handed out flowers to the mothers of people who had died there, next to the steel beams that rescue workers had found in the shape of a cross. When it came to asking someone to do the birthday flowers, he was an easy choice.

“They actually asked me if I would do the job and get paid for it,” he says, “and I told them I couldn’t take the money, that I’d donate the flowers.”

Over the years, Collarone says, he has met many of the victims’ family members. He tries to explain that he was there, and he tried to help as much as he could. But everything was so fast and so many were beyond help.

“You know, we couldn’t help them out on that day,” he says, “but I made sure we got them every other day on their birthdays.”