DAHLIAS
If you’re intrigued with the idea of growing flowers that can reach the size of dinner plates, consider planting dahlias. If you like diminutive flowers shaped like pompons, you can find these forms of dahlias, too.
Hundreds of named varieties of dahlia tubers will be available today at a special sale at the UC Irvine Arboretum as part of an arboretum open house this weekend. A dahlia demonstration garden with more than 300 named varieties is part of the arboretum’s plant collection.
Hybridizers have developed thousands of varieties of dahlias, with flowers ranging in size from one inch to one foot in diameter. The bushes range from compact, low-growing bushes that can be planted in containers or used for borders to plants that can reach six feet tall.
They’re classified by flower type, and the American Dahlia Society lists 12 distinct categories. They include decorative, cactus, semi-cactus, ball, pompon, anemone, collarette, orchid type and peony type. Flowers are also categorized by their sizes.
Dahlias are perennial plants, native to Mexico and its national flower. Members of Spanish expeditions discovered species growing in the Mexican mountains. Eventually, the tubers and seeds reached European botanists, and the plant was named Dahlia in honor of Swedish botanist Andreas Dahl. By the middle of the 19th Century, formal decorative, ball and cactus dahlias were being grown throughout Europe.
Hybridizers throughout the world have developed numerous strains. Today, there are more than 10,000 dahlia hybrids of various flower types. They are available in all colors except true blue.
Dahlias thrive in rich soil and full sun. In this region, they will do very well in coastal areas. Their popularity in Southern California has diminished, and many dahlia fanciers feel they deserve more recognition.
“Dahlias are easy to grow and there are many varieties that grow well in Southern California,” said Merle Robboy, M.D., of Corona del Mar. Robboy is an exhibitor, judge and past president of the Southern California Dahlia Society. He supervises the dahlia garden at UCI.
Dahlias may have developed a reputation for being time-consuming plants since many varieties require pinching and staking. Certainly, hobbyists who enter their dahlias in official competitions are very meticulous about pinching the growing shoots to produce the prized large-sized flowers. But that’s not a requirement and people who want to enjoy the flowers in their own gardens can forsake most of the pinching regimen.
Unlike their taller-growing relations, bedding dahlias don’t require staking. Like most flowering plants, removing the spent blooms encourages repeat blooms.
Dahlias can also be enjoyed as cut flowers. To ensure longer vase life, submerge the stems in several inches of very hot water for at least one
hour before arranging them.
They are dormant at this time of year, and this is the time to plan where to add them to a landscape, and to purchase tubers.
“I don’t advise buying dahlias from local nurseries because those packaged tubers are shipped from Europe and are very limited varieties,” Robboy said. “There are specialty growers in California and the Pacific Northwest who offer a large selection of excellent quality dahlias.”
Another good source for dahlia tubers as well as cultivation tips are local dahlia societies. The closest ones to Orange County are the Southern California Dahlia Society, which meets monthly in Long Beach, and the South Coast Dahlia Society, which meets monthly at the South Coast Botanical Gardens on the Palos Verdes Peninsula.
Although dahlia selection depends on one’s individual preference for flower size and form, Robboy suggests a few as some of the easiest to grow in this region: Alloway Candy (pink), Formby Perfection (purple), Lady Linda (yellow), Magic Moment (white with a touch of pink) and Mister Larry (large orange).
General dahlia care includes proper soil preparation before planting, fertilizing during the growing season and insect control.
Amend the soil before planting with liberal amounts of organic amendments such as planting mix or compost. Add a low-nitrogen fertilizer. Robboy uses one with a 5-10-10 formula since extra nitrogen promotes excessive foliage at the expense of flowers. Some experts also recommend adding some bone meal when the tubers are planted.
Tubers can be planted in March or April. Make holes one-foot deep and three feet apart for most varieties. The largest kinds can be spaced up to five feet apart. For the tall varieties that require staking, drive a five-foot stake into the hole, then place the tuber horizontally with the eye pointing toward the stake and two inches from it. Cover the tuber with three inches of soil. Gradually fill in the hole as sprouts appear.
Withhold water until the sprouts appear above the ground. Dahlias do not require a lot of water and will rot if the soil is too wet. Fertilize again when buds appear.
Tender dahlia shoots are tasty morsels to snails and slugs. These can be controlled by organic methods such as snail traps baited with beer, or by commercial snail baits. Aphids can also attack dahlias and can be eliminated by the regular spraying of soapy water or a chemical insecticide.
UC Irvine Arboretum is at Campus Drive and Jamboree Road, Irvine. Sale hours today are 10 a.m. to 2 p.m. Admission is $5 per person or free of charge to Friends of the Arboretum support group. Surplus dahlia tubers are sold for $1 each, and the proceeds are used to support the arboretum.
For information about dahlia societies, contact Robert Taylor of the Southern California Dahlia Society, (213) 425-1588 or Dick Kohlschreiber of the South Coast Dahlia Society, (310) 833-6823.
Dahlia Sources Almand’s Dahlia Gardens 2541 W. Avenue 133 San Leandro, Calif. 94577
Alpen Gardens 173 Lawrence Lane Kalispell, Mont. 59901
Camano Dahlias 2024 S. E. Harnden Road Camano Island, Wash. 98292
Connell’s Dahlias 10216 40th Ave. East Tacoma, Wash. 98446
Monterey Bay Dahlias 582 Powell St. Salinas, Calif. 93907
