Variety Show: Dahlias in the Spotlight
The past decade’s frenzy for fantastically diverse dahlias brings these summer-to-frost stunners from the back of the border to the front, plus into containers and bouquets.
Chocolate labs Ethyl and Oak playfully weave in front of Lisa Ringer as she wanders in a nature-meets-carnival atmosphere of big-top color created by nearly 1,500 lanky dahlia stems. She stops in front of a pink labeled ‘Gerrie Hoek', a variety she credits for sparking Two Pony Gardens at her rustic homestead near Long Lake, Minnesota. Here, this former flower child grows more than 100 dahlia varieties sold as tubers in spring and as cut flowers in summer and fall. "Their variety is amazing," Lisa says. "I saw a bumper sticker that read ‘Celebrate Diversity. Grow Dahlias.'"
Dahlia ‘Santa Claus' (left). Photos by Kim Cornelison.
Blooms come in all colors except true blue; sizes range from 2 inches to a 12-inch dinner plate. Classifications try to keep pace by grouping varied forms, such as ball, cactus, orchid-flowering, pompon and water lily to name a few. Add height variations of 1 to 8 feet, and you have a dahlia for every need.
Today's 50,000-plus dahlia varieties (five to 10 times more options than most flowers) descended from a few species growing wild in the high plains of ancient Mexico, where Aztecs used them for food and medicine. In 1789, Mexican botanists sent tubers to the Royal Botanic Gardens of Madrid, where their Spanish counterparts noted a versatile genetic structure. Mad hybridization ensued across Western Europe, yielding 14,000 cultivars before coming to the States at the end of the 19th century.
Dahlias last about a week in bouquets (left). "Never cut in the heat of the day," says Lisa Ringer (right). Place stems in a clean tall container of cool water, then remove an additional 2 or 3 inches of stem under the water, cutting at a long slant rather than straight across. "This gets rid of any air that prevents water from passing up the stem to the flower," Lisa explains. Photos by Kim Cornelison.
Though late to the party of a plant that originated next door, American gardeners now adore dahlia's exuberant color, carefree habits and summer-to-frost flowers.
As Lisa says, "Wherever they are, they command the spotlight."
Tender dahlia tubers won't overwinter in cold regions, so plant them as annuals or dig up and store over winter. Here are key growing tips.
1. Plant tubers in full sun once soil has warmed in late May or early June. For tall varieties, sink a stake or 5-foot section of rebar alongside the tuber; secure with tie tape as the plant grows.
2. Water regularly once foliage emerges, and mulch with at least 2 inches of compost or hay to keep shallow-feeding roots cool.
3. "Dahlias are the poodles of the flower industry because they need grooming," Lisa says. Trim away all but the strongest four to six stems when the plants are 6 inches tall. To encourage branching and more flowers, remove tops of the remaining stems once they have leaves.
4. After the first hard frost, carefully lift tubers from the soil with a spading fork and let them dry a day or two in the sun. Cover intact clumps with sand, sawdust, perlite or peat moss in large containers and store in a cool, dark, dry area.
5. Several weeks before planting in spring, separate clumps and use a sharp knife to divide stalks into divisions with an eye (growth bud).