Dahlia is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico.
There are 42 species and about 20,000 cultivars of dahlia.
This great variety results from dahlias being octoploids — that is, they have eight sets of homologous chromosomes, whereas most plants have only two.
Dahlias have mostly tuberous roots.
The stems are leafy, ranging in height from as low as 30 centimeters (12 inches) to more than 1.8–2.4 meters (6–8 feet).
Dahlias have leaves that can be different shades of green with a serrated edge. The leaves are pinnate for example the leaflets are arranged on either sides of the stem opposite each other.
Flower forms are variable, with one head per stem; these can be as small as 5 centimeters (2 inches) diameter or up to 30 centimeters (1 feet).
As a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right.
Like most plants that do not attract pollinating insects through scent they are brightly colored.
Dahlia’s display a vast array of hues, with the exception of blue.
These colorful spiky flowers generally bloom from midsummer to first frost, when many other plants are past their best.
Dahlias are considered one of the most spectacular garden flowers.
The official RHS (Royal Horticultural Society) classification lists fourteen groups, grouped by flower type: Single-flowered dahlias, Anemone-flowered dahlias, Collerette dahlias, Waterlily dahlias, Decorative dahlias,Ball dahlias, Pompon dahlias, Cactus dahlias, Semi cactus dahlias, Miscellaneous dahlias, Fimbriated dahlias, Single Orchid (Star) dahlias, Double Orchid dahlias and Peony-flowered dahlias.
Dahlias grow naturally in climates which do not experience frost, consequently they are not adapted to withstand sub-zero temperatures.
The dahlia is named after Swedish 18th-century botanist Anders Dahl.
Andres Dahl regarded it as a vegetable rather than a garden flower, but interest switched from the edible tubers to the blooms when the first varieties with large, double flowers were bred in Belgium in 1815. The word “double” simply designated flowers with more than one row of petals.
Their fleshy roots were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest.
Dahlias were first recorded by Westerners in 1615, when they were called by their Mexican name, acoctli.
They disappeared from record until 1787 when a botanical expedition ‘rediscovered’ them, and sent seeds back to their headquarters in Europe. Their existence was kept secret for another ten years however.
These plants quickly spread throughout the continent, being the favourite of the court of Queen Victoria.
The beauty of the dahlia flower inspired great symbolic meaning during the Victorian era and continues to be used today to express personal sentiments.
When given as a gift, the dahlia flower expresses sentiments of dignity and elegance. It is also the symbol of a commitment and bond that lasts forever.
The dahlia flower is used for flower arrangements to celebrate love and marriage.
The original French diva, Marie Antoinette, fell head over heels for dahlias when they were a new arrival in Europe, and now there’s a variety named after her [photo below].
In the mid 19th century a London newspaper offered £1 to the first breeder to produce a blue dahlia. The reward has never been claimed and breeders are still striving for the elusive blue color. There have been several near blue cultivars.
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine (a regional cuisine ofMexico).
It is the official flower of Seattle and San Francisco.
Dahlias can be used for dyeing. All dahlias (except the white flowers) produce warm yellows and oranges with an alum mordant and greens with iron mordants. A mordant is a substance that helps to fix the colors to textiles.
In Europe and America, prior to the discovery of insulin in 1923, diabetics — as well as consumptives — were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers.