Dahlias aren’t just your old-fashioned flowers anymore. The demand for dahlias has gone up, with a more than 40 percent increase in the number of dahlia tubers being shipped from Holland during the past five years, according to the Netherlands Flower Bulb Information Center. 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.

In Oregon, suppliers such as Swan Island Dahlias feature bloom festivals in summer and ship thousands of tubers worldwide during the growing season. Even the North Coast has celebrated the dahlia, with a parade held each summer in Seaside.

Dahlia colors range from demure pinks to splashy tropical reds and oranges – everything except true blue and black. Flower types range from mini to maxi, in shapes that recall daisies, cactus, pompons, waterlilies, buttons, zinnias and more. Once a favorite of Victorian gardeners, dahlias draw contemporary gardeners with their unique shapes, such as spidery orbs, and their interesting range of sizes, like the over-the-top dinnerplate varieties.

The best part for us about dahlias is that they come into their own during the days of late summer, perhaps our best time for growing big, bright flowers. They’ll keep blooming until frost, and in a mild winter, can stay in the ground until the next season. If you do dig your dahlias, it’s not difficult to keep them over winter as long as they’re healthy and dry.

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 come to flower in July and then continue to flower till the hard frosts of fall. 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.

Dahlias thrive on regular rainfall in most areas. 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 nine, dahlias can be treated as perennial hardy bulbs and left in the ground. In zones eight 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.

Here’s a brief primer on dahlia types, with some suggested varieties following.

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) and D. ‘Ludwig Helfert’ (bronze).

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) and D. ‘Orange Nugget’ (orange).

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) and D. ‘Pomponette’ (pink).

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) and D. ‘Purpinka’ (purple-pink).

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) and D. ‘Esther’ (bronze-orange with yellow).

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.

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).

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. 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 – 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. ‘Cafe au Lait’ (cream with light brown edging), D. ‘Duet’ (deep red with white tips), D. ‘Kenora Macob’ (deep red) and D. ‘Fleural’ (white).

Cathy Peterson belongs to the Clatsop County Master Gardener Association. “In the Garden” runs weekly in Coast Weekend. Please send comments and gardening news to “In the Garden,” The Daily Astorian, P.O. Box 210, Astoria, OR 97013 or online to peterson@pacifier.com

Plantsman gives talk on Great Plant PicksSCAPPOOSE – Richard Hartlage, the current director of the Elizabeth Miller Botanical Garden and The Great Plant Picks program, gives a talk, “The Best Bet Plant Program,” at Joy Creek Nursery, 1 p.m., Sunday, April 27.

Hartlage, who plans to leave the Miller Botanical Garden soon to pursue landscape design, will present many of the plants that have been selected by the Great Plant Picks committee. The committee, which is sponsored by the Elizabeth Miller Botanical Garden, was created to evaluate perennials, shrubs and trees for the gardener in the Pacific Northwest.

The owners at Joy Creek Nursery say this is a great opportunity to hear “this fine plantsman before he leaves this position.” The event is free.

Joy Creek Nursery, founded in 1992, includes four acres of display and educational gardens showcasing extensive collections of perennials and shrubs in a variety of garden settings. The nursery hours are 9 a.m. to 5 p.m. For more information, call (503) 543-7474 or visit the Web site www.joycreek.com