The flowers seem stolen from a storybook, with pink pompoms sprouting next to flame-colored orbs and lavender pinwheels. In one of San Francisco’s oldest gardens, a group of summer camp children recently squealed as they marveled at rings of yellow petals larger than their heads.

Throughout the late summer months, eyes widen and phone cameras click as visitors delight in the dahlias of San Francisco.

“It’s hard to believe they’re real sometimes,” said Deborah Dietz, 75, as she got on her knees to inspect a petite purple blossom in the Dahlia Dell, the garden that is in Golden Gate Park.

Compared with roses and orchids, dahlias are far wilder and more varied, appealing to lovers not of perfection but of wonder. And they have captured San Francisco’s imagination for generations.

In the early 1900s, the city built a reputation as one of the best places in the world to grow dahlias, which are native to Mexico. There were yearly dahlia competitions at the gilded Palace Hotel, where a prized tuber could sell for as much as $15, then equivalent to three days’ wages.

The San Francisco Board of Supervisors in 1926 named the dahlia the city’s official flower, celebrating its hardy nature, immigrant roots and unmatched “gayety and color.”

“In its versatility, its beauty, its infinite variety of color and form, it is the very symbol of San Francisco life and of the spirit of her people,” the proclamation reads.

That was long before televisions, jet engines or smartphones, and in the hundred years since, San Franciscans moved on to other pursuits. Yet, in today’s world of doomscrolling, climate anxiety and A.I. uncertainty, dahlias are once again en vogue.

Timothy Wong, 37, began growing dahlias in San Francisco six years ago and now spends more hours than he will admit with his hands in the dirt. His friends have been inspired by him to raise them, too, and he has noticed a younger crowd beginning to attend the local dahlia society’s tuber sales and annual show.

“Flower farming is everyone’s dream escape from daily life now,” said Mr. Wong, who recently started a popular new dahlia garden in the city.

In the early 1900s, several commercial dahlia growers operated in the western half of San Francisco when it was still just sand dunes. Later, families planted dahlias in the backyards of the narrow homes built in what came to be known as the Sunset and Richmond districts adjacent to Golden Gate Park.

Dahlias are originally from the highlands of Mexico, so they struggle in many parts of the United States with extended freezes or temperatures exceeding 85 degrees. They thrive, however, in the well-draining soil and cool weather of the Bay Area, where climate extremes are tempered by maritime fog.

“A lot of people think San Francisco’s a pretty nice place to live — a lot of plants think that, too,” said Isaac Lichter Marck, a plant ecologist who studies the sunflower family, which includes dahlias, at the California Academy of Sciences.

Dahlias peak in August and September and don’t wither until late fall, with an internal clock left over from when they would bloom after late summer monsoons in Mexico, Mr. Lichter Marck said. The unique timing is another reason gardeners love them — they blossom just as other summer flowers wind down their annual show.

On a recent afternoon at the Dahlia Dell, a man set up a folding table in the shade, facing the flowers. He dipped his brush in a watercolor kit.

“For dahlias, there’s nothing in the world like this,” said Kevin Woodson, a painter who splits his time between Taiwan and Oakland, Calif.

Dahlias have been grown in Golden Gate Park since the 1880s, and the dell is currently tended by seven volunteers, each of whom is assigned a section to plant and take care of. Dahlia varieties have names as whimsical as their forms, including Kung Fu Kitty, Fuzzy Wuzzy, Boogie Nites and I’m a Hottie.

The flowers’ unusually high number of chromosomes allows them to pull off a kind of botanical magic trick, transforming a dahlia garden into what appears to be a riot of different flowers in all shapes and sizes. Sarah Smith, 60, cupped in her palm a bloom resembling a pink-and-white daisy. Next to her was a dahlia with flowers that mimicked red carnations.

Ms. Smith, a retired third-grade teacher who lives in the Sunset District, recalled getting hooked on dahlias about five years ago when she became responsible for her own patch in the dell. Tending to the plants felt like a respite from a world that increasingly divided one’s attention, she said.

“Looking at every stem, every leaf, every bud, every everything, and the hours would just fly by, and it was so therapeutic to just be in that space,” she said. “It’s the opposite of sitting in front of a screen.”

The culture around dahlias often involves sharing plants and growing tips, and distributing stunning cut flowers. Ms. Smith and other dahlia fans said they saw it as an antidote to San Francisco’s reputation these days as a cradle for tech companies minting billionaires.

At the Dahlia Dell, bakers, doctors and file clerks alike donate their time to create something beautiful for the public to enjoy at no cost.

Ms. Dietz, a retired pharmaceutical sales representative who has been planting dahlias in the dell for more than 30 years, shows her flowers at the city’s annual dahlia competition every August. It is the floral equivalent of a Westminster Kennel Club Dog Show, where blooms are judged on countless characteristics such as petal shape, stem stiffness and leaf size. With a gloved hand, she touched the small rosy petals of Elvira, one of her favorite dahlias, which she called “the most beautiful Chihuahua at the show.”

Ms. Dietz welcomes a few volunteers each year who want to learn how to care for the flowers. Dahlias force one to work at their speed, and there’s something that feels right about getting down in the dirt with them, she said.

As Ms. Dietz gardened at the Dahlia Dell, a tourist fed her Labrador treats to get him to sit in the exact right position to photograph beside the brightest pink blossoms.

Another woman walked past the garden, distracted by her phone. Then she stopped abruptly. She turned, looked over and just stared at the dahlias.

Produced by Jenni Lee and Matt Ruby.