Dahlia is a mix of bushy, tuberous, herbaceous perennial flowering plants indigenous to Mexico & Central America. A member of the Compositae family of plants, its garden relations include the sunflower, daisy, chrysanthemum, and zinnia.

There are forty-two species of dahlia, with hybrids generally grown as garden flower plants. Flower forms are variable, with each stem having one flower; those can be as small as 5 cm (2 in) breadth or up to 30 cm (1 ft) (“dinner plate”).

The stems are leafy, varying in height from as little as 30 cm (12 in) to over 1.8–2.4 m (6–8 ft). The majority of varieties do not produce scented flowers. Like most plants that do not draw pollinating insects through scent, they are vividly coloured, displaying most hues, except for blue.

The dahlia was listed the national flower of Mexico in 1963. The tubers were cultivated as a food crop by the Aztecs, but this use mostly died out after the Spanish Conquest. Efforts to introduce the tubers as a food crop in Europe were unsuccessful.

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What Does a Dahlia Flower Look Like?

Dahlias are perennial (Plants that live more than two years) plants with tuberous roots, though they are planted as annuals in some regions amidst cold winters. While some have herbaceous stalks, others have stems which become woody in the absence of secondary tissue & resprout following wintertime dormancy, providing further seasons of growth.

As members of the Asteraceae(a wide variety or family of flowering plants), the dahlia has a flower head that is a composite (hence the older name Compositae) with both central disc florets & surrounding ray florets.

Every floret is a flower in its own right although is often mistakenly described as a petal, especially by horticulturists. The modern name Asteraceae refers to the presence of a star with circling rays.

The History of the Dahlia Flower

Early history

Spaniards reported discovering the plants growing in Mexico in 1525. Still, the earliest known record is by Francisco Hernández, physician to Philip II, who was ordered to attend Mexico in 1570 to study the “natural produce of that country”.

They were produced as a food source by the native peoples, & were gathered in the wild & cultivated. The Aztecs used them to treat epilepsy, & employed the long hollow stem of the (Dahlia imperalis) for rainwater pipes. The indigenous peoples inconsistently identified the plants as “Chichipatl”” (Toltecs) & “Acocotle” or “Cocoxochitl” (Aztecs).

From Hernandez’s perception of Aztec to Spanish, within various other translations, the word is “water cane”, “water pipe flower”, “waterpipe”, “hollow stem flower” & “cane flower”. All these lead to the hollowness of the plants’ stem.

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Hernandez described two species of dahlias (the pinwheel-like Dahlia pinnata & the huge Dahlia imperialis) and other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo aristocrat who followed Hernandez on the part of his seven-year investigation, made a series of drawings to enhance the four-volume report.

Three of his drawings pictured plants with flowers. Two of the flowers looked like the modern bedding dahlia, & one resembled the species Dahlia merckii; all displayed a high degree of doubleness.

In the year 1578 the manuscript, titled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was shipped back to the Escorial in Madrid. They were not translated to Latin by Francisco Ximenes until the year 1615.

In 1640, Francisco Cesi, President of the Academia Linei of Rome, obtained the Ximenes translation, & after interpreting it, printed it in 1649–1651 in 2 books as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The first or original documents were destroyed in a large fire in the mid-1600s.

European Introduction

In the year 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, on his way to Mexico to steal the cochineal insect prized for its scarlet dye, described the strangely beautiful flowers he had observed growing in a garden in Oaxaca.

In 1789, Vicente Cervantes, Director of the Botanical Garden in Mexico City, sent “plant parts & specimens” to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles blossomed one plant the same year, then the second one a year later. In the year 1791, he called the new growths “Dahlia” for Anders (Andreas) Dahl.

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The initial plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia Rosea for its rose-purple colour. In the year 1796 Cavanilles flowered a third plant from the parts shipped by Cervantes, which he called Dahlia coccinea for its scarlet colour.

In the year 1798, Cavanilles shipped D. Pinnata seeds to Parma, Italy. In that year, the Marchioness of Bute, the Earl of Bute’s wife, the English Ambassador to Spain, owned a few seeds from Cavanilles & shipped them to Kew Gardens, where they flowered but were lost after 2 to 3 years.

In the following years, Madrid shipped seeds to Berlin & Dresden in Germany, & to Turin & Thiene in Italy. In the year 1802, Cavanilles sent tubers of “these three” (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at the University of Montpelier in France, Andre Thouin at the Jardin des Plantes in the city of Paris & Scottish botanist William Aiton at the Kew Gardens.

In the same year, John Fraser, English nurseryman & later botanical collector to the Czar of Russia, brought D. coccinea seeds from the city of Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse the following year, providing Botanical Magazine with an illustration.

In the year 1804, a new species, Dahlia sambucifolia, was successfully cultivated at Holland House, Kensington. Whilst situated in Madrid in 1804, Lady Holland was delivered either dahlia seeds or tubers by Cavanilles.

She shipped them back to England, to Lord Holland’s librarian Mr Buonaiuti at Holland House, who triumphantly raised the plants. 12 months later, Buonaiuti produced two double flowers. The plants grown in the year 1804 did not survive; the new stock was brought from France in 1815. In the year 1824, Lord Holland sent his wife a letter, including the following verse:

“The dahlia you brought to our isle.

Your praises forever shall speak;

Mid gardens as sweet as your smile,

And in colour as bright as your cheek.”

In the year 1805, German naturalist Alexander von Humboldt shipped more seeds from Mexico to Aiton in England, Thouin in Paris, & Christoph Friedrich Otto, manager of the Berlin Botanical Garden.

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More importantly, he sent seeds to botanist Carl Ludwig Willdenow in the country of Germany. Willdenow now reclassified the quickly growing number of species, alternating Dahlia’s genus to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata & D. rosea under Georgina variabilis; D. coccinea was still held to be a different or separate species, which he renamed Georgina coccinea.

How Did Dahlia Flowers Get Their Name

The naming of the Dahlia plant itself has long been a matter of some confusion. Many references state that the name “Dahlia” was given by the pioneering Swedish botanist & taxonomist Carl Linnaeus to honour his late student, Anders Dahl, author of Observationes Botanicae.

Nevertheless, Linnaeus passed away in 1778, more than 11 years before the plant was introduced into Europe in 1789, so while it is commonly agreed that the plant was titled in 1791 in honour of Dahl, who had died two years before, Linnaeus could not have been the one who did name the beautiful flower.

It was most likely Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid. They should be credited with the attempt to scientifically define the plant genus or family since he not only received the very first specimens from the city of Mexico in the year 1789 but named the first 3 species that flowered from the cuttings.

Despite who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, declaring that the genus Dahlia Thunb. (published a year after Cavanilles’s genus & now viewed a synonym of Trichocladus) was more widely accepted, changed the plants’ species from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a teacher at the Imperial Academy of Sciences of St. Petersburg, Russia.

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He also reclassified & renamed the initial three species grown, & classified, by Cavanilles. It was not until the year 1810, in a distributed article, that he officially chose the Cavanilles’ original designation of Dahlia. However, the name Georgina persisted in Germany for the next several decades. In Russian, it is still Georgina георгинa.

“Dahl” is a homophone (each of two or more words having the same pronunciation but different meanings, origins, or spelling, for example, new and knew.) of the Swedish word “dal”, or “valley”. However, it is not an accurate translation, and the plant is sometimes called the “valley flower”.

Dahlia Flower – Where Do They Grow?

Dahlia is located predominantly in Mexico, but some species are found reaching as far south as northern South America. D. australis occurs at least as far southward as southwestern Guatemala.

At the same time, D. coccinea & D. imperialis also occur in portions of Central America & northern South America. Dahlia is a family of flowering plants of the uplands & mountains, being situated at elevations between 1,500 & 3,700 metres, in what has been described as a “pine-oak woodland” vegetative zone. Most varieties have limited areas spread throughout many mountain ranges in Mexico.

Dahlia Flower Ecology

The most prevalent pollinators are bees & small beetles.

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Dahlia Flower Pests and Diseases

Slugs & snails are severe pests in some parts of the world, especially in spring, when new growth is appearing through the soil. Earwigs can also damage the blooms. The other main pests likely to be found are aphids (ordinarily on young stems & immature flower buds), red spider mite (causing foliage mottling & discolouration, worse in hot & dry situations) & capsid bugs (ending in contortion & holes at growing tips).

Diseases that affect dahlias include powdery mildew, verticillium wilt, grey mould, dahlia smut, phytophthora & some plant viruses. Dahlias are an origin of food for the larvae of some butterfly and moth species including angle shades, ghost moth, common swift, & sizeable yellow underwing.

Dahlia Flowers – Where Do They Like To Grow

Dahlias grow freely in climates that do not encounter frost. Consequently, they are not able to withstand sub-zero temperatures.

However, their tuberous nature gives them the ability to survive periods of dormancy, & this trait means that gardeners in temperate climates with occurring frosts can cultivate dahlias successfully, provided the tubers are taken from the ground & stored in cool yet frost-free conditions during the wintertime or cooler months.

Planting the dahlia flower tubers quite deep (10 – 15 cm) also provides some shielding. When in the flowers are in active growth, modern dahlia hybrids function most favourably in well-watered yet free-draining soils, in locations receiving plenty of sunlight.

Taller cultivars ordinarily require some form of staking as they grow, & all garden dahlias need deadheading repeatedly, once flowering begins.

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Dahlia Flowers Facts

Do Dahlias come back every year?

Dahlias, on the other hand, are perennials. In their natural warm climate, they re-sprout from their underground tubers to flower each year.

Do Dahlias like sun or shade?

Select a sowing site with full sun. Dahlias grow more flowers with 6 to 8 hours of uninterrupted sunlight. They love the morning sunlight the best. Choose a spot with a bit of shelter from the wind.

How do Dahlias grow in Australia?

Dahlias grow most desirable in moist, well-drained soil with full morning sun, afternoon shade & shelter from winds. Before planting the tubers, you can improve the soil by digging in well-rotted organic matter such as compost, leaf mould & chicken or cow manure. Stake tall growers when you are planting them to not damage the tuber.

Do Dahlias multiply?

Dahlia tubers are sometimes called a “bulb”, but they are technically a tuber, comparable to a potato. Underground, the tubers increase each year (again, like the potato plant). You only require one tuber with one “eye” to successfully grow a robust dahlia plant.

What month do you plant Dahlias?

Plant dahlia tubers outside after your last frost date, when the soil has warmed. The flowers like warmer months and are not tolerant of frost. Most dahlias will start flowering by midsummer. Suppose you live in a cold climate & desire to get an early start. In that case, you can plant your dahlia tubers in pots and leave in a protected position such as an area that is covered but also has plenty of sunlight.

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If You Would Like To Buy Or Purchase Some Dahlia Flowers or Seeds:

Further Reading

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