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Dahlias: Tropical Tubers Ride Crest of Flower Fashion Wave
by Netherlands Flower Bulb Information Center
May 11, 2003

Tropical plants and late season flowers are two powerful fashion trends in the garden. Riding high on this dual wave are dahlias, trendy tubers that splash tropical color across the landscape from mid-summer till the hard frosts of fall. Once a favorite of Victorian gardeners, these drama queens from south of the border have burst back onto the scene, bedding down in America’s most à la mode gardens.

Indeed, demand for dahlias has gone through the roof, with exports from Holland, a major supplier, up 40% over the past five years, according to statistics from the Netherlands Flower Bulb Information Center (NFBIC) in New York City.

“Dahlias certainly fit into America’s continuing passion for tropical plants, but I think the dahlia fascination is more focused on the beauty of the flowers themselves and their role as a color anchor in the garden,” said Sally Ferguson, NFBIC director since 1989.

“What’s more,” added Ferguson, “dahlias are in full swing during one of the most pleasant periods to enjoy the garden: late summer and fall. American summers can be brutal. The flowers can take the heat, but can the gardener? I think that’s what’s behind the popularity of late-blooming flowers. And dahlias, not only bloom late into the season, they thrive in fall! And they keep blooming until frost knocks them out.”

There’s Something about Dahlias

With flower types that range from mini to maxi, in shapes that recall daisies, cactus, pompoms, waterlilies, buttons, zinnias and more, dahlias offer a diversity of shapes, sizes and colors second only to tulips. Official registries list thousands of named varieties, in all colors under the sun except true blue and black.

Dahlias are tender summer bulbs (tubers, to be exact). They grow quickly and flower effusively, reaching their dramatic peak in the sun-dappled months of autumn. As tender bulbs, dahlias are sensitive to frost and cannot be planted outdoors until the threat of frost has passed. For a fast start-up, plant dahlia tubers indoors in pots in late winter/early spring then plant outdoors when the weather warms. In late spring, dahlia tubers can be planted right into garden beds or large containers just as one would plant tulips or daffodils in the fall.

Dahlias can also be purchased as bedding plants, professionally pre-grown in nursery pots. As demand increases, nurseries are offering a broader range of potted plants including dahlias and other sought-after summer bloomers such as cannas, caladiums, begonias, and exotics such as gingers, pineapple lilies, and elephant ears.

Dahlias in the Garden

Dahlias come to flower in July and then continue to flower till the hard frosts of fall. They are perfect for bed or border and make excellent container plants. They’re also a must for that area of the garden reserved for producing cut flowers. In fact, dahlias are great for cut flowers no matter where you plant them; for the more you cut dahlias, the more flowers they produce. If you want your dahlias to provide maximum blooms, it’s recommended that you pinch and discard the spent flowers.

Dahlias come by their love of fall weather naturally. They hail originally from the high mountain regions of Mexico and Guatemala. Bathed in Pacific Ocean breezes, these high regions are cool. Dahlias like cool weather and, after blooming all summer, they’ll continue to bloom happily throughout the fall season. First brought to Europe by the Spanish conquistadors, dahlias’ rich colors and cool habits took the royal courts of 18th century Europe by storm. Today’s high-performance dahlias are having a similar effect.

Today’s Dahlias

Modern dahlia flowers range in size from dwarf to giant, from blossoms small as teaspoons to flowers as big as dinner plates. They’re available in a vast array of lively colors and are virtual flower factories, blooming from mid-summer through fall. Based on acreage under cultivation in Holland, the most popular dahlia color is red, followed by pink/salmon, yellow, white, orange/apricot, lilac/purple and purple-violet. As for flower shape, there’s a dahlia to suit just about any taste. Dahlias have been so successfully bred over the centuries that they are today divided into many groups. Here are those groups of most importance to home gardeners:

Cactus and Semi-Cactus – Both types have double flowers with long pointed ray flowers that revolute or roll back along half their length, giving the flowers a spiky look. Most cultivars reach a height of more than 40 inches. Among the most popular are: Dahlia ‘Alfred Grille’ (salmon pink with a yellow center), D. ‘Purple Gem’ (cyclamen purple), D. ‘Ludwig Helfert’ (bronze), D. ‘My Love’ (creamy white), D. ‘Kennemerland’ (yellow), D. ‘Firebird’ (yellow with red tips).

Decorative – These are double dahlias with broad, flat-tipped petals that are sometimes wavy. The flowers are normally large and the plants easily top 40 inches tall, though there are even taller varieties. Cultivars to watch for include: D. ‘Duet’ (red with white tips), D. ‘Lucky Number’ (lilac-purple), D. ‘Berliner Kleene’ (old rose), D. ‘Rosella’ (violet-rose), D. ‘Orange Nugget’ (orange), D. ‘Snowstorm’ (white) and D. ‘Golden Emblem’ (deep yellow).

Pompon – Also double flowered, these dahlias have globe-shaped, relatively small flowers. The petals form little tubes that revolute or roll back along their entire length. Though there are exceptions, pompons normally grow to more than 40-inches tall. They are tough and extremely resistant to bad weather. Among the most popular are: D. ‘Nescio’ (blood-red), D. ‘Franz Kafka’ (lilac-pink), D. ‘Pomponette’ (pink), D. ‘Natal’ (purple with velvety blush), D. ‘New Baby’ (orange), D. ‘Schneeflocke’ (white), and D. ‘Deepest Yellow’ (yellow).

Ball – Similar to Pompons, but the flowers are larger and less spherical. Among the most popular are: D. ‘Red Cap’ (blood-red), D. ‘Bonny Blue’ (lilac-pink), D. ‘Doris Duke’ (light salmon), D. ‘Peter’ (purple), D. ‘Maren’ (orange) and D. ‘Golden Torch’ (yellow).

Anemone-flowered – As the name implies, these look somewhat like anemones. They have one or more rows of flat (not revoluted) petals arranged in a wreath. They are relatively short, averaging around 15-inches tall. Favorites include: D. ‘Brio’ (orange-red), D. ‘Purpinka’ (purple-pink), D. ‘Siemen Doorenbosch’ (magenta-pink with a purple blush), D. ‘Honey’ (two colors, old rose and sulfur yellow) and D. ‘Toto’ (white).

Collarette – These are small to medium flowers with large flat ray petals surrounding an open center. Within the ray and surrounding the center is a wreath of shorter petals, often of a different color: this forms the “collar.” These varieties range in height from 12 to 35 inches. Cultivars to consider include: D. ‘Alstergruss’ (orange-red with yellow collar), D. ‘Hartenaas’ (pink with white collar), D. ‘Esther’ (bronze-orange with yellow collar), D. ‘Brides Bouquet’ (white with white collar), D. ‘Walhalla’ (purple-red with white collar) and D. ‘La Gionconda’ (red with lemon-yellow collar).

Mignon – Favorites of many garden enthusiasts, these delicate dahlias have single, open flowers with prominent yellow disc flowers in the center. The plants range in height from 12 to 20 inches. Examples include: D. ‘Roodkapje’ (red), D. ‘Mies’ (lilac-pink), D. ‘G.F. Hemerik’ (orange-red) and D. ‘Yellow Sneezy’.

Peony-flowered – These dahlias have semi-double flowers with an open center. For many years the most popular Peony-flowered dahlia was a cultivar called D. ‘Bishop Llandaff’, an heirloom variety that dates back to 1927. It has open deep-red flowers with nearly black, mahogany foliage. Meanwhile, another semi-double with dark foliage is emerging as a favorite: D. ‘Fascination’, a cultivar with rich violet-rose flowers. It grows 30- to 40-inches high.

Topmix – These are dwarf dahlias, with heights around 10 to 12 inches and tiny flowers only an inch or inch-and-a-half across. Cultivars include: D. ‘Scura’ (orange-red with dark leaves) and D. ‘Sweetheart’ (pink and white).

Other groups of dahlias include Single-Flowering, Water Lily and Orchid. Also, there are new groups of dahlias that are quickly growing in popularity. They include:

Dahlianova – Double-flowering varieties with a wide variety of colors available. They average 8 to12 inches tall. Cultivars include: D. 'Arizona’ (orange) and D. 'Virginia’ (yellow).

Gallery – This series contains cactus and decorative varieties which generally grow to 12 to 24 inches tall. Examples include: D. 'Rembrandt' (pink), D. 'Art Deco’ (bronze yellow with a red center), D. 'Leonardo' (peach with a touch of red).

Impression – These are small colarette dahlias suitable for bedding and perfect for use in pots on balconies and patios. Depending on the variety, height can range from 12 to 20 inches. Varieties to look for include: D. 'Festivo' (red with white-tipped flowers in the collar), D. ‘Fortuna' (deep yellow with orange center), D. 'Fuego' (red with yellow center).

Dinner Plate Dahlias – Often large-flowering dahlias are found at retail under the name “Dinner Plate Dahlias.” This is not an official classification, in fact these robust dahlias are registered under several different classifications, but nonetheless all are huge and magnificent. Popular varieties include: D. ‘Babylon Bronze’ (golden orange), D. ‘Café au Lait’ (cream with light brown edging), D. ‘Duet’ (deep red with white tips), D. ‘Kenora Macob’ (deep red) and D. ‘Fleural’ (white).

Dahlia Care

Dahlias thrive on regular rainfall in most areas though will require watering in arid and desert climates. Pinching off or cutting spent flowers is recommended. The stalks are woody, so aphids can attack them. A spray with insecticidal soap or even physically washing the aphids off a few times with a strong jet of water usually solves this. In USDA zone 9 dahlias can be treated as perennial hardy bulbs and left in the ground. In zones 8 and below, dahlias either need to be lifted and stored for winter or treated as annuals with new tubers or bedding plants planted each spring. With the wide range of colors, sizes and flower types available, there’s truly a dahlia for every garden. In fact, most gardens could find a use for lots of dahlias, in beds, borders, containers, just about anywhere that would benefit from robust flower color from summer through fall.

Article and Photo courtesy Netherlands Flower Bulb Information Center


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