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Of Dahlias, Devoted Growers, and their High-Stakes Competitions

Many gardeners take their flowers seriously; few devote almost all their time to growing one breed—the dahlia—then drive hundreds of miles to go mano a mano against other fanatical growers, for nothing more than a blue ribbon. But that’s exactly what Deborah Dietz does.

Issue: Spring 2022

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Volunteer Steven Dibner started helping tend the Dahlia Dell in San Francisco’s Golden Gate Park 20 years ago. Dibner was a non-gardener when he began, but early on, Dietz saw he “great hands for gardening.” Then she learned he is the associate principal bassoonist for the San Francisco Symphony.

Written by THOMAS COOPER
Photography by JAK WONDERLY

  1. The Dahlia Dell
  2. Floral Tinkering
  3. The Lottery
  4. The Competition
  5. The Secret Sauce

In 2019, the World’s Largest Dahlia, as judged by the American Dahlia Society (ADS), was a bloom of the cultivar Maki, which measured 14-7/8 inches across. Maki is among the group commonly—and in the case of some people, disparagingly—known as dinner-plate dahlias. The award-winning flower was grown by Iris Wallace, a member of the Monterey Bay Dahlia Society in Central California. In a photograph, Wallace is holding a bloom the size and bulk of a large throw pillow. Its petals are a creamy pink streaked with raspberry flashes. If she held it at shoulder level, you would not see her head.

I discovered this horticultural behemoth when browsing the bulletin of the American Dahlia Society, which has some 2,600 members distributed among 58 local societies including Monterey. The ADS preside over all rules and regulations from judging of flowers and judging of judges (a 64-page guide sets out the details), to the clarification of dahlia flower types and the registration of new plants. The dahlia grows in 21 different floral forms and 10 sizes, just one indication of the genus’ chameleon qualities. There are self-descriptive forms such as cactus, waterlily, pompom, and peony. Other types are less revealing: collarettes, which resemble daisies; mignon single; orchette. Lest there be confusion about what you’re looking for in, say, a cactus type, the ADS is clear: “Cactus types have long, pointed ray florets with petal edges that are involute, revolute (edges rolled back), or straight, radiating out from an open center in a somewhat spiky look.” Finally, there are the “novelty” flowers, which have “characteristics that fall outside the other classifications.” The ADS guide for 2022 lists 2,087 recognized varieties. To make the list they must have won at least three blue ribbons at shows in two growing seasons.

Volunteer gardener Deborah Dietz, shown here at San Francisco’s Dahlia Dell, cuts the flowers not fit for show purposes and donates them to a local library and senior center. She also leaves some in buckets on her front porch; neighbors know it as the best florist in town. photo by Jak Wonderly
Deitz works much of her magic from her home in San Francisco’s unusually sunny Bernal Heights neighborhood. “I love how my little greenhouse looks like a spaceship nesting down for the evening.” photo courtesy of Deborah Dietz

Deborah Dietz’s favorite blue-ribbon winner is Elvira, which Dietz, a member of the Dahlia Society of California and the American Dahlia Society, describes as “a pink, peony form”—rarely getting more than 18 inches tall, with flowers “barely as big as a quarter.” She calls the Elvira “an open-centered flower” resembling a daisy, aster, or zinnia. “She likes to grow,” Dietz says. “A single plant can have 100 flowers in bloom at one time.” In 2021, Elvira was the winningest dahlia at ADS shows nationally.

There are 42 species within the genus dahlia, all native to upland regions of northern South America, Central America, and, predominantly, Mexico. There are reports that the Aztecs employed the leaves for medicinal reasons, hollowed out stems to pipe water, and used the flower in decorative arts. The Dahlia first appears in Western manuscripts in the mid-16th century, in the accounts of a Spanish botanist. Botanically, they are classified as composites, making them relatives of daisies, cosmos, sunflowers, and asters. One species, D. imperialis, the tree dahlia, grows 20 to 30 feet tall. It throws out pendant flowers of lavender and muddy pink that are more cosmos than the intricate blooms of modern hybrids. There is also a vining dahlia, D. Macdougalii, with aerial roots like those sprouted by certain orchids. It was named by Scottish plant hunter George Sherriff, who identified the new species in 1950 in Oaxaca, Mexico.

“Dahlia tubers have long been eaten in Mexico,” Dietz told me. She is not a fan. “I’ve had them pan-seared like French fries and shredded like zucchinis for zucchini bread. Anything will taste ok with enough sugar, oil, and eggs. But most are vile.”

Elvira has been the winningest dahlia for Dietz, who has grown the flower for 15 years. Why? Each 18-inch-tall plant produces hundreds of blooms, so the odds of ribbon-worthy flowers are great. Dietz trains her volunteers on Elviras. “With so many flowers, a mistake doesn’t ruin the show.” photo by Jak Wonderly

The Dahlia Dell

Dietz can recite these details and many more with the exactitude of a professor and the enthusiasm of a frontier preacher. Her bubbling laugh is quick, and she will talk dahlias as long as you have questions. Dietz has been growing and showing dahlias in San Francisco since 1986. “I was just gobsmacked,” she says of the first plant she raised. Since 1993, she has led the corps of volunteers that manage Dahlia Dell, a public display garden in San Francisco’s Golden Gate Park.

Behind the scenes, at Dietz’ home: “Every space is covered by dahlia gear. Our big Society tuber and cutting sale is April 30, so this is all staging ground right now.” photo courtesy of Deborah Dietz

Sheltered by surrounding Monterey cypress, eucalyptus, and an assortment of other evergreens, some dating to the Park’s original transformation from sand dunes to green landscape in the 1870s, the Dahlia Dell is a teardrop some 145 feet long and 45 feet across at its widest point. In its season, which runs from June through October, the Dell’s central bed holds, just barely, some 500 dahlias. There are pompoms in chalk white, bawdy red cactus types, lavenders, corals, bi-colors, chiffon yellows, dark burgundies, corals, orange petals with central bosses of sunburst yellow—all shimmering above a sea of green foliage.

A Victorian style fence encloses the garden; visitors steady themselves on the top railing to photograph the display or to ward off dizziness brought on by the colorful audacity of the scene. More than 5 million people visit the Dell annually, coming in cars and buses, also by foot, bike, rollerblades, and wheelchair. One day, Dietz recalls, several buses appeared, four teams of square dancers emerged, swirled briefly, and departed.

With Dietz’s guidance and encouragement, six fellow Bay Area dahlia fanciers—she refers to them as “donors”—each take a slice of the garden and fill their sections as they wish, planting 700 plants altogether. Dietz says that sense of ownership tends to give the gardeners “…pride of kingdom. Things look much better than if it was a communal effort.” The group includes Lou Paradise, one of the most prominent dahlia breeders in the Bay Area, and a radiologist who looks for varieties that hold up well when cut (“he takes them into the hospital,” Dietz says). For her part, Dietz grows 19 of the 21 dahlia forms in her area, so she can use the plot for educational purposes. “People from all over the world get to enjoy plants that have never been seen,” she says.

The teardrop-shaped Dahlia Dell garden at a rare, quiet moment. Such a prolonged profusion of bloom demands lots of feeding: Dietz adds compost to all her planting holes, and once the plants are established, she gives them a foliar feeding twice a month. photo by Jak Wonderly

Floral Tinkering

In 1846, Edinburgh’s Caledonia Horticultural Society announced a prize of £2,000 for the creator of a blue dahlia. To date, no one has been able to claim the award.

With the gardener’s version of a toolbelt around her waist, her gray-flecked, shoulder-length hair held in place by a broad red visor, Dietz can be found in the garden three or four days a week between May and November. Once the aspiring tubers have been planted, there is staking and disbudding (to encourage the plant to put its energy into larger blooms), watering and feeding, weeding, and deadheading of spent blossoms. If you do not see Dietz, consider looking at ground level; she may be on hands and knees collecting flowers that have dropped since her last visit, or checking for slugs or signs of powdery mildew disease, a common affliction in the foggy San Francisco climate. “Good flowers,” she likes to say, “demand great attention to detail and tinkering.”

Dietz took charge of the Dell after the gardener who had been there since World War II fell ill and couldn’t carry on. “The Park tried,” Dietz says, “but nobody knew anything about dahlias. They spent a lot of money on junk and couldn’t even fill up the Dell.” So Dietz and a fellow member of the San Francisco Dahlia Society, Erik Gaensler, donated some of their leftover tubers. “When everything started blooming, and theirs look like your granny’s old, ratty dahlias, and ours looked like soldiers and ballerinas, they said, ‘What’s the difference?’ The difference was that we only grow competition dahlias.”

Hillside plantings adjacent to the central teardrop garden, as seen in mid-September. Flowering begins in May and peaks in August to September. Blooms will persist through Christmas. photo by Jak Wonderly
An as-yet-unnamed seedling raised by Lou Paradise makes its first public appearance at the Dell. If it shows promise, he will grow it for four years to test its genetic stability. photo by Jak Wonderly

The Lottery

If you are drawn to breeding new flower forms, colors, or foliage, the dahlia is a willing subject. The process starts in the fall, with letting some blooms go to seed, literally, and collecting the seeds when ripe. The next season, you sow those seeds. Although some growers transfer pollen with fine paint brushes, many prefer to let the bees handle the cross-pollinating. Unlike most plants, and all humans, both of which are diploids (having two sets of chromosomes), dahlias are octoploids—creatures with eight sets of chromosomes. This greatly accelerates the introduction of new traits among the flower’s offspring—one reason, no doubt, that a research team at Auburn University is engaged in a multiyear project to sequence the dahlia genome.

Seeds, says Deitz, “are kind of like lottery tickets. You grow 100 seedlings, and 90 percent get thrown on the compost heap.” The few with promising flowers (“you’re only looking for flowers”) you grow for a second year, and maybe a third. At the end of the fourth year, you get to name a seedling and send tubers to one of the ADS trial gardens, where they are grown anonymously. Judges come from around the country, and if a plant receives an average score of 85 (out of 100), it becomes an accepted American Dahlia Society dahlia. The society’s registry of names would provide extensive fodder for a challenging game of charades: Dorothy’s Slipper, Grandma’s Hug, Fancy Pants, Valley Porcupine, Kung Fu Kitty, Hollyhill Black Widow, Kenora Wildfire.

Bumble Rumble, a collarette type of dahlia, grows to 4 feet in height and produces an abundance of 3-inch-wide flowers. Deborah Dietz, ever the perfectionist, considers this particular bloom “a bit blowsy for show… the pollen is showing in the center and staining some of the petals, and the coloring on the petals is not even.” photo by Jak Wonderly

In 1846, Edinburgh’s Caledonia Horticultural Society announced a prize of £2,000 for the creator of a blue dahlia. (Although the plant is pronounced DAY-lee-ah in the British Isles, the correct pronunciation is DALL-ya, as the plant was named, in 1791, by the Director of the Royal Botanic Gardens of Madrid, in honor of Andreas Dahl, a Swedish botanist and student of Carolus Linnaeus—also a Swede, and famous for creating a hierarchical, binomial system of classifying organisms that is still the basis for naming plants and other organisms from orcas to humans.) To date, the reward has not been claimed, as blue is not part of the genus’ genetic makeup. But dahlias come in almost every other color and form, with 200 or so new varieties coming online every year. Swan Island Dahlias of Canby, Oregon, the largest dahlia grower in the U.S., offers 376 varieties in its 2022 catalog and will send off some 800,000 tubers—what some British refer to as a chicken leg, because of a resemblance to a knobby drumstick—in the spring shipping season, according to Nicholas Gitts, Swan Island’s owner.

Orchettes are the most recent flower form to gain recognition by the ADS as a distinct group. This lavender-rose cultivar is rightly named Fancy Pants. Attractive to bees and butterflies, it grows some 30 inches in height. photo by Jak Wonderly

Swan Island grows all its tubers, plus 12,000 seedlings for evaluation, on 45 acres of fertile bottomland in the Willamette Valley. After the plants are harvested and cleaned of soil, a team of 30 workers perform a loaves-and-fishes act on each clump, dividing the larger, dense clumps into smaller pieces, each with one or two “eyes,” nodes that will produce the coming season’s flowers in a customer’s garden. The blind tubers (those that lack flower-producing eyes) and those that are damaged are useless; Gitts’ father used to feed them to a small herd of cattle he tended. “The cows went wild for them,” Gitts recalled. More recently, the tuberous chaff was sold to a California company that made a coffee substitute called DaCopa. I asked Gitts if dahlias are part of his diet, and he said no. “They’re really, really bland.”

Swan Island’s nursery was purchased in 1963 by Gitts’ parents. His father, Nick Sr., is now a very popular dahlia, which the Swan Island catalog describes as follows: “11-inch gorgeous red blooms with petals that ruffle and turn, showing off the golden buff reverse on the backside of each petal. Strong, sturdy plant with a very upright growing habit which will reach 5 feet in height. Outstanding exhibition variety.”

Dietz spends a lot of time at ground level—gathering spent flowers that have fallen; checking for slugs; and taking off lower leaves, which provides better air circulation among the plants, thereby reducing the chance of disease. photo by Jak Wonderly

The Competition

To Dietz, the difference between garden variety dahlias and those that are show-worthy is like “the difference between a pedigreed racehorse and the nag that your grandmama keeps feeding in the back lot,” she says with a chuckle. Yet retail growers aren’t particularly keen on show dahlias, since they generally produce fewer tubers than their retail cousins. “It’s kind of like those Russian mothers that got ribbons for having 18, 19, 20 children,” Dietz says. “They were not always Einsteins, but there were a lot of them.” For those few plants that are exceptional, however, there is no end of devotion. Dietz knows a 92-year-old gardener who raises dahlias in a public park in San Leandro, a hobby that has also made him a collector of golf umbrellas, used to shield the plants from little bits of grit in the air. That, and the extra shade offered by the umbrellas, apparently yield very clean petals with colors that are more vibrant. “His plants are astonishing,” Dietz says. “But when you look at his garden it looks like the umbrellas of Cherbourg.”

KA’s Cloud is an informal, decorative flower introduced by breeder Kristine Albrecht of Santa Cruz Dahlias. The plants grow 4 to 5 feet tall and produce flowers that are a whopping 8 to 10 inches across. photo by Jak Wonderly

Dietz transports her flower entries in a Honda sedan she calls her Dahliamobile, which she has managed to stuff with 280 cut blooms, along with shovels, buckets, and 130 aspiring dahlia “clumps.”

Dietz generally attends four shows a year, each time taking some 200 blooms from which she’ll select 100 or more to exhibit. For a show that begins on a Saturday, she starts picking flowers around 5 p.m. on Friday night, and picks for 2 to 3 hours. Selecting blooms with blue-ribbon potential from among hundreds of plants, each laden with bloom, takes a sharp eye and a hard heart. Unlike Britain’s National Dahlia Society, which does not require flowers to be shown with foliage, the ADS rules call for one set of leaves per stem (“that shows garden competence,” says Dietz). Are these flowers open enough? Are they too open? Is the color clear and consistent? Are the petals arranged evenly? The leaves healthy, with good color? The considerations are endless.

Stored overnight in her garage in buckets of water, the dahlias are loaded in the morning into her Honda Element, a small sedan that she refers to as the Dahliamobile. (“I have transported as many as 280 cut blooms at one time, but that was 50 or 60 too many to keep them all in good condition.”) She’s also managed to stuff this car with as many as 130 caged dahlia clumps (the cages protect them from gophers), dug from the Dell for winter storage, along with shovels and buckets and other gardening supplies. Not surprisingly, many of Dietz’s peers modify their vehicles specifically for dahlia transport, but even that’s no guarantee of protection. Dietz recalls one show where “someone had five magnificent, huge, white dahlias—it was going to be superb. He had to slam on his brakes during the drive to the show. His wife walked into the hall with two in her hair and three in her hands like a bride. They had to be enjoyed one way or another. Really, it was more of a funeral than a wedding.”

These semi-cactus flowers, called Eden Patricias, produce a spectrum of sunset shades from pink to rose, with a butter-yellow central blush. Developed by Dell gardener Lou Paradise (hence the name “Eden”), the plant is also named for another of the Dell’s seven donors: 84-year-old Patricia Hunter. photo by Jak Wonderly

The Secret Sauce

Since most shows are on weekends, judging typically begins Saturday morning around 10 a.m. If you aren’t local, she says, “you could have been on the road since 8 a.m. Friday morning. You probably stayed up overnight putting your flowers in vases to get them on the show bench in the right place. A lot of people are pretty blurry.” But adrenaline still runs high. “The first buzz at a show is ‘what’s out there, what’s new, what’s cool’?” Dietz says. “People invariably head right to the seedling bench because that’s our future.”

The setting for a dahlia show is nothing like the Dell. You start with a sterile ballroom at a Sheraton Inn, say, or the conference room at a community college. Set up ranks of lunchroom folding tables, add three or four hundred dahlia blooms at the peak of their cosseted existence, and the scene comes to life. The effect is of a massive fireworks display stopped in midair, with explosions of pink, white, coral, yellow, rose, burgundy, bicolors, and blends. At varying heights and in dimensions from the diameter of a quarter to the span of a hefty cantaloupe, each dahlia is near perfect in its conformation, as set down in the ADS Guide to Judging Dahlias.”

One of Dietz’s favorite bicolor dahlias is Irish Blackheart. The flowers are only 4 to 6 inches across (Dietz describes them as “little jewels.”) Introduced in 2014, Irish Blackheart has won 28 medals at American Dahlia Society (ADS) shows. photo by Jak Wonderly
The unabashed orange semi-cactus flowers of AC Ben will span 10 inches or more. These plants grow to 4 feet tall on sturdy stems, but Dietz still likes to stake each stalk for protection against the SF Bay Area’s punishing winds. photo by Jak Wonderly

If a team of judges is standing, say, before a stem of All That Jazz—a formal, decorative plant—here’s what they want to see: “The ideal depth is three-quarters the diameter of the bloom and should not be greater than its diameter.” And that’s just for starters. “People talk this time of year about their ‘secret sauce’,” says Dietz, referring to the special ingredient exhibitors mix into their growing medium to supercharge their plants. “One fellow takes the detritus from 19 owl houses,” she says, “and mixes it in the compost he puts in his planting holes. His secret sauce has all the droppings—crispy corpses and other stuff—contained in the pellets the owls cough up.”

The lure of ribbon-worthy blooms can drive growers to great lengths. “Judges look for attitude—the way the flower is ponied on the stem,” says Dietz, who is herself also a senior dahlia judge, “not looking at the sky or the ground. You want a 45-degree angle, perfect for looking at. Some competitors make little cotton balls and tuck them under the chins of the flowers while they are developing and remove them just before the judges arrive.” Occasionally growers tie their flower stems to thin dowels, securing them with pipe cleaners, in order to produce stems with ramrod posture. Come show time, the crutches must be tossed aside.

The culmination of a show is the judging of the head table. All the flowers that have been awarded blue ribbons are brought together, and the judges—usually a panel of seven—choose one as best in show. It is a nervous time, says Dietz. “You don’t want to make any noise or do anything that might give away which is your dahlia, or that you have one that’s on the line. You’re biting your tongue and crossing your fingers and saying to yourself, ‘yes, this is my year.’” She has twice won best open-centered (flowers in which the central disk is fully exposed) and once captured overall Best in Show with a flower from Hollyhill Cotton Candy, a large, cactus-like flower with swirling petals of deep, saturated pink.

Dietz, demonstrating the proper head-tip of an award-winning dahlia, stands next to her section of the Dell. In the background is San Francisco’s Conservatory of Flowers, architectural centerpiece of Golden Gate Park. Opened in 1879, it is the oldest wood-and-glass public conservatory in North America. photo by Jak Wonderly

When all is judged and done, what most surprises Dietz about dahlias, she says, “is that they can make me gasp over and over and over again. I’ve done this for 30 years; you’d think I’ve seen a dahlia. And another one will open, and it’s like my heart stops for a moment.” Dietz once traded 100 tubers to get two. “I won,” she says, “I didn’t need those 100 tubers, but I really wanted the novelty form called Horse Feathers. It looks like a white dandelion whose head has exploded. Michael Pollan posed the question, do we grow plants, or do plants convince us to grow them? Dahlias have some of us in thrall.”

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Tips and Inspiration from England’s Great Dixter Gardens

The Drought Fighter

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