To keep track of the thousands of varieties available today, the American Dahlia Society classifies the flowers according to color, flower size, and form. The largest blooms (classed as AA) can reach 14 inches or more across, while the smallest ones (Pompon and Mignon Single) bear flowers as small as 2 inches across.
The shape of the petals (called ray florets) determines the flower formation. Here we list dahlia flower forms, along with the favorite varieties of three Western dahlia specialists - Erik and Gerda Juul, Jennifer Eubank of Swan Island Dahlias, and Kim Connell of Connell's Dahlias - and their comments about them.
FORMAL DECORATIVE: Flat petals are uniform and arranged like shingles on a roof. 'Almond Joy' (lavender and white blend); good, strong stems. 'Canby Centennial' (deep rose red); named in honor of the 100th birthday of Canby, Oregon; 'Vernon Rose' (variegated pink and dark red); "everybody's favorite."
INFORMAL DECORATIVE: Petals are twisted, curled, or wavy, and their arrangement is irregular. 'Dana' (bright orange red with a bright yellow center); "very showy in the garden." 'Gitts Perfection' (delicate pink blending to white); "absolutely gorgeous show winner." 'San Francisco Sunrise' (very bright orange); outstanding color, good for cutting.
SEMICACTUS: Petals are broad at the base and rolled for up to half their length. 'Camano Regal' (purple); "exceptional flower." 'Dare Devil' (bright red); excellent cut flower. 'Kenora Sunset' (red and yellow blend); "very popular color," good for cutting.
CACTUS: Petals are rolled for more than half their length, straight or slightly curved downward; they radiate in all directions from the center. 'Glenbank Twinkle' (white and purple); "striking in the garden." 'Ruskin Marigold' (orange); "new, good in every way."
INCURVED CACTUS: Petals are rolled for more than half their length and curved upward. 'Bird's Nest' (pink); "swirls like a Ferris wheel - very interesting." 'Lilac Mist' (white blending to lavender); excellent in the garden and as a cut flower.
FIMBRIATED OR LACINIATED: Petals are split on the ends, giving the flower a fringed look. 'Al Almand' (orange); striking color. 'Fidalgo Climax' (clear yellow); "unusual shaggy look." 'Nenekazi' (red and pink blend); "beautiful color." 'Show 'N' Tell' (red tipped with yellow); "very showy like its name."
BALL: The fully double flowers are ball shaped and more than 3 1/2 inches wide. 'Jessie G' (dark red); lots of blooms, great color, good for cutting. 'Kenora Fireball' (silvery red); striking color, good form. 'L'Ancresse' (white); excellent cut flower. 'Robin Hood' (orange and pink blend); unusual color combination.
MINIATURE BALL: It is like Ball but smaller, between 2 and 3 1/2 inches wide. 'Downham Royal' (dark purple); "beautiful color." 'Robann Royal' (lavender); a popular variety.
POMPON: Also similar to Ball, but blooms are less than 2 inches in diameter. 'Poppet' (orange); beautiful color, good in the garden. 'Yellow Baby' (yellow); a favorite for arranging.
WATERLILY: Fully double blooms look like saucers from the side. The center should be closed. 'Juul's Lotus' (white blushed with lavender); "beautiful in bouquets." 'Snowflake' (pure white); one of the best whites for cut flowers. 'Wildwood Marie' (pink with yellow center); "beautiful colors."
PEONY: Open-centered flowers have two or more rows of petals surrounding a disc. 'Longwood Dainty' (orange); "a winner." 'Powder Gull' (pink); "a winning flower." 'Tasagore' (dark red); very striking green-black foliage.
ANEMONE: One or more rows of single petals surround a pincushion-like dome. 'Alpen Pearl' (lavender, yellow, and white blend); "stands out in the garden and at shows." 'Goldie Gull' (yellow and pink); "another winner."
COLLARETTE: A single row of evenly spaced petals are a backdrop to smaller disc flowers emerging from the center. 'Alpen Cherub' (pure white with yellow in center); strong stems, prolific bloomer. 'Astrid Siersen' (purple and white); "a favorite with the public." 'Cher Ami' (red and yellow); small, "perfect bloom."
SINGLE: A single row of petals surround the center disc. 'Bashful' (deep purple with lavender tips); "it glows." 'Joshua Juul' (white, orange, purple blend); "very unusual color combination." 'Juul's Cosmos' (lavender); "unique color for a single - looks like a cosmos flower."
MIGNON SINGLE: Similar to Single, but it is under 2 inches in diameter. 'Matthew Juul' (orange and dark red blend) and 'Rembrandt' (dark red); "both are good for small gardens - as border plants or in pots."
ORCHID: Blossoms have a single row of tubelike petals. 'Juul's All-Star' (dark red), 'Juul's Star' (white), and 'Marie Schnugg' (red); "all have excellent form and color and are good for arranging."
NOVELTY: This is a dahlia that doesn't fit in any other class. 'Alloway Candy' (pink); a beautiful cut flower.