The ‘Dahlia Dome’ Olympics are coming to Portland – here, Oregon

If variety is, as the 18th-century English poet first said, the spice of life, then dahlias are undoubtedly the spice of the horticultural world.

With more than 20 different shapes, ranging from semi-cactus to dahlia to minion, blooms from 1 inch to 16 inches across, over 20,000 species and many, many more colors than the average rainbow, it’s no wonder the plants have such a growing, loyal following.

And those followers will descend on Portland — at least, those who don’t already live here — for the American Dahlia Society’s National Show Aug. 24-28 (which is open to the general public for free Aug. 26-27) at the Holiday Inn Hotel and Conference Center. Portland Columbia Riverfront.

The display attracts serious — as serious as flying across the country with your prized dahlias flying by your side — dahlia lovers and those just curious about plants featuring the lush, colorful blooms that seem to appear everywhere this time of year.

“The show (which was also held in Portland in 1968 and 2012) is considered the dahlia Olympics,” said Larry Smith of the Portland Dahlia Society, who has been growing dahlias for more than 30 years. “The Northwest is one of the world’s premier climates for growing dahlias, and some of the most successful hybridizers in North America operate in this region.”

Nicholas Gates, who heads the family that has run what is now the country’s largest dahlia-growing business since the early 1960s — Swan Island Dahlias in Canby — is one of those hybridizers. He has a problem that many business owners would like to face: trying to keep up with increasing demand.

“The popularity seems to continue to grow,” he said. “We had to increase warehouse space, purchase additional land to grow dahlias, and we are under construction for our gift shop and offices.”

Swan Island Dahlias is in the midst of the annual Dahlia Festival, which draws crowds to Canby to see acres and acres of gorgeous deadhead dahlias and decide which ones they want to try for themselves.

While Gates thinks big when he looks at the future of dahlias, Smith thinks small.

As in micro.

“There’s some really good new stuff,” he said, and he should know. He grows 25-30 micro varieties, with flowers less than two inches in diameter. “They are very easy to grow in pots, don’t take up a lot of space, and the open-centered types are great pollinators.”

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Why dahlias?

It is clearly the diversity that has sparked interest in the amazing plants that begin their existence as underground tubers.

Modern hybridization has “created an amazing diversity of dahlia varieties,” Smith explained. “Blooms range in size from up to 16 inches in diameter to miniature varieties less than 2 inches across. (But) the real beauty is that they keep on giving,” they bloom from early June through November, with proper care.

Gates agrees.

“People are drawn to dahlias because of the long bloom period, the range of flower sizes and the amount of flowers the plants produce,” he said.

Mark Oldenkamp of Canby, president of the Portland Dahlia Society and vice president of the national organization, was first drawn to dahlia hortensis 40 years ago, when his wife, Laura, suggested they visit Swan Island dahlias.

“I wasn’t keen on going, but once I went, I came back the same week,” he admits now.

He now grows 600 plants, 250 varieties, cuts about 1,500 seedlings a year, and has gained a reputation as a dahlia evangelist.

He is also at a very high level in the upcoming national show.

The big show

There will be plenty of “eye candy” filling the Holiday Inn’s 18,000-square-foot grand hall, Oldenkamp said. It is estimated that 5,000 flowers will be displayed.

“If you go to the exhibition you will see a love for the varieties you will want to grow and learn how to grow them,” he said.

One of those talking about best practices for growing dahlias will be Deborah Dietz, curator of Dahlia Dell, a much-visited collection in San Francisco’s Golden Gate Park. She’s sharing some of her extensive knowledge at 1:30pm on Saturday.

Some of the best hybridizers in the business, including Ted Kennedy of Hollyhill Dahlias in Oregon City, will be on hand to answer questions.

For members of the American Dahlia Society who register for the show — the serious growers mentioned above — there will be judging, socializing and a trip to several local nurseries.

Including Swan Island Dahlias of course.

How to grow dahlias

The following is from Larry Smith, a member of the Portland Dahlia Society who has been growing dahlias since 1992, and (Tips 5-6) from a previous interview with Heather Gates Schloe of Swan Island Dahlias.

• Plant the tubers in the spring, around the same time you plant tomatoes.
• Plants love sun, so make sure they get at least six hours of sun per day. The color will be more vibrant if the growing area provides partial shade during the afternoon hours.
• Plant them in well-drained soil to prevent the tubers from rotting.
• Add well-rotted compost before planting.
• During the dry season, water deeply twice a week, and more often during periods of extreme heat.
• If you dig up the tuber in the fall, wait until after the killing frost. Store the tubers in a cardboard box or moss-covered box where the temperature is between 45 to 50 degrees. It has a thin skin, so do not place it on a concrete floor, as it will draw moisture from the tuber. You may need to mist it to keep it slightly damp but not wet.
• Divide in spring. Dig the tuber and let the wound heal overnight before replanting.

When purchasing

• You can purchase tubers and plants at the Portland Dahlia Society’s annual sale and auction in April and May, but they are also available at garden stores and online. Two of the most popular growers are local: Swan Island Dahlias in Canby and Holyhill Dahlias in Oregon City.
• Where to buy. Be careful when purchasing tubers from supermarkets. There is no guarantee that you will get the variety shown on the label, and sometimes during the growing season you will find that the resulting plants are sick.
• Be especially careful about imported Dutch tubers, many of which have been shown to be infected with dahlia gall, which can contaminate the soil and spread among dahlia plants.

– Larry Smith

The most popular

Larry Smith’s list includes varieties that are easy to grow and fairly easy to obtain. Anything bearing the Hollyhill label, hybridized locally, is very popular and hardy.

• Hollyhill “Black Beauty”: Medium-sized casual décor in dark red.
• Hollyhill ‘Jitterbug’: A small species of orange-like cactus.
• “Chilson’s Pride”: Casual mini decor in pink.
• “Pooh”: orange and yellow collar.
• “Elvira”: a dark pink, small peony type.
• ‘Inflammation’: Small orange single with a compact growth habit, ideal for growing in pots or in a small area.
• ‘Citron de Cap’: A light yellow frilled (frilled petal) variety.
• ‘AC Ben’: A giant orange cactus-like plant.
• “Cornell”: Red fireball type.
• ‘Parkland Rave’: Curved cactus with lavender.

Tips for cutting flowers

From a column by Dennis Beck and Marcia Westcott Beck in The Oregonian/OregonLive that first ran in 2016. Information taken from Heather Gitts-Schloe of Swan Island Dahlias.

1. Place the cut stems in 2-3 inches of hot water. The water temperature should be 160-170 degrees on a candy thermometer or bubbles should just be starting to form at the bottom of the pan.

2. Keep it in water for an hour in a plastic or metal vase (not glass).

3. This method opens the cut plants to become free drinkers, and flowering continues for up to seven days.

4. The stems will darken as they were in the hot water. You can either cut off the dark part or leave it.

5. Use normal temperature water after the initial hot water bath.

2023 American Dahlia Society National Show

What: The American Dahlia Society’s annual gathering, with people coming from all over North America and as far away as Australia.

When: August 24-28 for registered attendees; Open to the public August 26-27; Noon-5pm Saturday, 10am-4pm Sunday

Where: Holiday Inn Portland Columbia Riverfront Hotel & Conference Center, 909 N. Hayden Island Drive, Portland

Cost: There is no admission fee

HIGHLIGHTS: Deborah Dietz, who oversees Dahlia Dell next to the Conservatory Building in Golden Gate Park, will talk about how to grow dahlias at 1:30 p.m. Saturday.

More information: portlanddahlia.com

Swan Island Dahlias

What: The largest dahlia grower in the United States, with more than 375 varieties covering nearly 50 acres, hosts the annual Dahlia Festival.

Where: 995 NW 22nd Ave., Canby

When: August-September

Cost: There is no admission fee, although there will be food trucks and bouquets for sale, in addition to items in the Swan Island gift shop.

More information: dahlias.com