One flower, infinite beauty

"Do good or bad and it all comes out the same," he says. "I won best in show as a novice."

Therein lies the true beauty of the dahlia: its ability to flourish in Southern California and the abundance and diversity of its glorious blooms. Experts believe that all modern dahlia hybrids — an astonishing 58,000-plus varieties at last count — are derived from only two of three species that made their way from Mexico to Spain in 1789 and to other parts of Europe in the early 1800s, where they were hybridized.

Today, most collectors shun local bulb sources, especially big-box stores. Instead, they trade with other hobbyists and buy from specialty growers in Oregon and Washington.

"It's dahlia heaven up there," says Dick Kohlschreiber of San Pedro. He and other members of the South Coast Dahlia Society maintain a collection of 150 varieties at the South Coast Botanic Garden on the Palos Verdes Peninsula. "We can grow beautiful dahlias, but it's more of a struggle in this climate."

Although dahlias require warmth, Southern California's intense summer sun makes them swoon. For this reason, most collectors live along the coast.

Mae and Bruce Keith grow dahlias at their Palos Verdes Estates home — she for 54 years, he since retiring 25 years ago. They planted "only" 40 varieties this year. "They're beautiful and lovely to show, but you can't just stick them in," Mae says. "You have to cultivate, stake, fertilize, spray for diseases and insects, disbud to one flower per stem."

When scorching days precede a show, the Keiths shade the flowers — especially reds, pinks and lavenders — with beach umbrellas to prevent fading.

Saturated colors, extraordinary shapes and hypnotic symmetry are only part of what make dahlias remarkable. They're also resilient when cut, lasting up to a week if the vase water is changed daily. (Devotees insist that dahlias must be harvested often for repeat bloom.) Alas, the only thing they seem to lack is fragrance.

The genus Dahlia belongs to the daisy family, or Asteraceae, characterized by composite flowers with a center of disk florets surrounded by petal-like ray florets. Cosmos, coreopsis and bidens are its closest relatives.

All 35 Dahlia species are native to the highlands of Mexico and Central America, where volcanic soil and nutrient-rich forest debris promote rapid growth during warm, wet months. Most are low- to medium-size perennials with green or red-purple foliage that dies in winter.

One rare species, D. macdougalii, is an epiphyte (air plant) that scrambles over rain forest trees and festoons them with long roots. The so-called tree dahlia, Dahlia imperialis, one of the few species available to gardeners, is a gigantic tropical herb with huge divided leaves, bamboo-like stems that can surge to more than 20 feet in one season, and lavender or white flowers in November.

The Aztecs called the dahlia "acocotli" and "cocoxochitl" and used the tubers, often called the "roots," for food and medicine. Francisco Hernandez, who sailed from Spain to Mexico in the 16th century, wrote that roots of the dahlia tasted "smelly, bitter and sharp … hot and dry in the third degree." Europeans of that period were not interested in it.

But during the 19th century, a period dubbed "dahlia-mania," European breeders produced thousands of hybrids. Dahlias, plant breeder Cunningham explains, have 64 chromosomes, far more than most flowers. The complicated genetics provide seemingly infinite variation.

The ball-shaped dahlia, perfectly rounded with dozens of ray florets swirling out from a tightly closed center, was developed in 1818. It was followed by the pompon, the cactus, the anemone, the peony and the waterlily. Star and orchid emerged in the 20th century, along with floriferous dwarf dahlias ideal for bedding and containers.

The American Dahlia Society's classification system — the so-be-it of judged dahlia shows — identifies 19 flower forms, nine sizes (from less than 2 inches to more than 10) and 15 colors (no blue or black).

Dahlia tubers are modified underground stems that store water and nutrients during lean times. They are elongated like potatoes but with a single "eye" at one end.

Planted in spring and grown kindly, dahlia tubers work their magic, yielding foliage, buds and blossoms in 60 days. They can grow and flower through the long days of summer into autumn.

Dahlias prefer well-amended, fast-draining soil; raised beds are strongly advised. During the growing season, these leafy plants also need plenty of fertilizer and water. Think daily irrigation plus overhead spritzes during a heat wave. "They're heavy feeders," Kohlschreiber says. "We usually recommend a high-nitrogen fertilizer until the buds are formed and showing some color. Then we switch to a 'high bloom' formula, such as 2-10-10."