Dahlia Terminology


Dahlia 'Spartacus', a red informal decorative type

The American Dahlia Society (ADS) defines the terms by which Dahlias are classified and judged. Dahlias are described based on formulas such as "B-LC-R", meaning a flower of size B (medium sized), of type laciniated cactus, and of color red. Another example would be "A-WL-LB W/P", meaning a flower of size A (large sized), of type water lily, and of color light blend with pink. More information may be found on the ADS Homepage. The ADS recognizes the following categories based on size, type and color; we've added stem color and leaflet number:

Size
Examples
AA
 Flower heads over 10 inches in diameter Giant
A
 Flower heads between 8 and 10 inches in diameter Large
B
 Flower heads between 6 and 8 inches in diameter Medium
BB
 Flower heads between 4 and 6 inches in diameter Small
M
 Flower heads up to 4 inches in diameter Miniature
BA
 Flower heads between 3.5 and 4 inches in diameter Ball
MB
 Flower heads between 2 and 3.5 inches in diameter Minature Ball
P
 Flower heads up to 2 inches in diameter Pompom
MS
 Flower heads up to 2 inches in diameter Mignon Single
 
BA, MB, P, and MS also relate to the flower type, for which please see below

 

Examples
Type
Ray florets (petals) are flat, partially revolute (petal edges roll back), or partially involute (petal edges roll forward). The petals are uniform and regularly arranged, tending to curve toward the stem.
Ray florets are twisted, or curled, or wavy creating an affect that the petals are not flat. The petals may be partially revolute with their arrangement appearing irregular.
The ray florets are broad at the base, straight, incurved or recurved and the ray florets revolute for up to one-half of their length.
Cactus
(C)
The ray florets are revolute for more that one-half of their length; they also may be pointed, straight, or recurved, radiating in all directions from the center of the flower head.
The ray florets are curved for more than one-half of the length but the pointed petals have a pronounced curvature toward the center of the flower head.
The split or laciniation should be in proportion to the ray floret length. There should be an overall twisting in the area of the split involute or revolute ray florets, to give a fringed effect.
Ball
(B)
Fully double flowers, ball shaped or slightly flattened at the face, where the ray florets are blunt, rounded, or indented, involute for most of their length, fully involute for about one-half their length, and normally displayed in a spiral arrangement.
Same form as ball, differing only in size.
Pompom
(P)
Fully double flowers similar to ball dahlias but more globular and smaller in size; the ray florets are involute for their whole length and fully involute for more than half of their length.
Stellar
(ST)
Fully double, breaking gradually from immature florets to fully developed outer florets. The outer florets should be narrow and involute with a slight recurve to the stem. The less mature florets should possess the same narrow and partially involute characteristic. The depth of the stellar dahlia type should be from one half to two thirds the diameter of the bloom, the greater depth being the ideal.
Fully double and symmetrical blooms with a side view that appears to be flat or saucer shaped. The ray florets are openly faced giving the bloom a delicate appearance. The center is closed and dome shaped breaking gradually to four to seven rows of fully developed outer ray florets which are also broad and slightly cupped.
Paeony
(P)
An open centered dahlia with two or more rows of ray florets surrounding the disc flowers. Ray florets adjacent to the disc flowers may be smaller, twisted, or curled.
Anemone
(A)
One or more rows of ray florets are surrounding a center of elongated tubular disc florets. These disc florets should be fully developed and present a domed, pincushion appearance.
An opened centered dahlia with a single row of uniform evenly spaced compound ray florets in a flat plain surrounding the disc flowers. The petaloids that surround the disc are less than one-half the length of the ray florets.
Single
(S)
An open centered dahlia with a single row of uniform evenly spaced ray florets in a flat plain surrounding the disc flowers.
Same as single, differing only in size.
Orchid
(O)
An open centered dahlia with a single row of evenly spaced ray florets in a flat plain surrounding the disc flowers. The ray florets are involute for two-thirds or more of their length and fully involute for at least one-third of their length.
Dahlias with characteristics differing from the present classifications. These dahlias will have a disc center.
Dahlias with characteristics differing from the present classifications. These varieties will have a fully double center
 
Please note that mature petals are used to determine the form

 

Examples
Color
ADS WH-1 to WH-9; some green, grey or brown caste acceptable
ADS YL-1 to YL-24; some with green caste; YL-24 appears orange
ADS OR-1 to OR 24; oranges with more red tones
ADS PK-1 to PK-24; light in color
ADS DP-1 to DP-24; more red tones
ADS RD-1 to RD-24; more true or "blood" reds
ADS DR-1 to DR-12; more maroon tones
ADS LV-1 to LV-24; shades of purple towards blues
ADS PR-1 to PR-36; a wide variety of purples, including red tones
ADS LB; blooms with mixtures of rather than well-defined lighter white, pink and purple colors; occasionally these are further specified using "w/", implying "with" followed by a predominating color.
ADS BR-1 to BR-24; oranges with heavy brown tones
ADS FL; blooms with mixtures of oranges, reds, yellows, and bronzes without purple or white tones; occasionally these are further specified using "w/", implying "with" followed by a predominating color.
ADS DB; blooms with mixtures of rather than well-defined darker purple, pink, and red colors; occasionally these are further specified using "w/", implying "with" followed by a predominating color.
ADS V; blooms with two or more colors appearing on the face of the bloom either in dots, splashes, stripes on narrow lines; usually the colors are referenced in the formula, such as "M-C-V-pk/y".
ADS BI; blooms with two distinctly clear and sharply separated colors. ; usually the colors are referenced in the formula, such as "A-C-BI-pk/y".
 

 

Stem Color

Green,
No visible anthocyanins -

Anthocyanins are absent from the stem, and no "sun-tanning" of the stem occurs with long-term light exposure.

Example - 'Inland Dynasty'

Green,
Anthocyanins light dependent -

Anthocyanins are clearly present in the stem, and stem color darkens or "tans" with long-term light exposure; greenhouse-grown plants may retain green stems.

Examples - 'Jim Dandy' & Seedling 04TS8

Tan,
Some anthocyanins present -
Anthocyanins will be clearly visible in the stem under all conditions, but not in the concentrations evident in purple-stemmed plants.

Example - 'Ben Huston'

Purple,
High anthocyanin content-

Stems with high anthocyanin content; these varieties are typically bred for dark stem color and originate with the cultivar 'Lucifer' from 1884.

Examples - 'Magenta Star' & 'Smooth Operator'

 

Leaflet Number
Dahlia leaves are divided into smaller parts, called "leaflets"; this condition is called pinnate. Typically, leaflet number can be correlated with how close the cultivar is to a species; species have higher leaflet number, generally. In some cultivars, the leaflets themselves are further divided; this is termed bipinnatifid, meaning "almost doubly pinnate"
Dahlia leaflets are usually dentate, meaning that they have teeth. The "sharpness" of the teeth is defined by being either acute (sharp) or obtuse (blunt or rounded); the "size" of the teeth is described as being broad (large) or narrow (small). If sharpness or size modifiers are absent, the leaflet can be considered "average" among dahlia cultivars.
'Al Almand' has broadly dentate leaves with acute teeth, and 3-5 leaflets.
'Woodbridge' has bipinnatifid leaves with acute teeth.