My garden boasts a Vulgar Border…not full of plants that swear but of brightly coloured one – clashing pinks, oranges, purples and yellow which almost make your eyes water. And chief amongst them are dahlias. Dozens and dozens of them. So as it’s in full technicolour flood at the moment I thought I’d write about the history of dahlias. A straightforward task you might think, and so did I when I started. I thought the most difficult thing to do would be to keep personal feelings [prejudices?] about them under control. But I was wrong.
I thought knew the outlines of the dahlia story but as it turns out there’s quite a lot of myth even in that basic storyline. 
Worse still the garden dahlia has a tortured taxonomy and complex family history. Despite all the best efforts of botanists the real story is still uncertain and even trying to understand the Wikipedia version left me confused. But don’t worry I’m not going to even try to explain it, although there are some references in case you suffer from insomnia or like labyrinthine puzzles and want to try and figure it out yourself.
By the way if you hate dahlias the post is worth reading anyway for the stories of the people involved, and if you love dahlias then read on to discover their convoluted history…
The dahlia is almost a weed in its native Mexico and central America, growing rather surprisingly in upland areas mainly between between 1,500 and 3,700m [ie higher than Ben Nevis!] but where, although frost is common, the ground does not freeze. Most species appear to be generally shade-intolerant, and grow in woodland clearings, among rocky outcrops, and then opportunistically anywhere sunny especially in places where the ground has been disturbed. They are naturally mainly single flowers although there are some which are occasionally semi-double.
For more about dahlias in the wild follow this link!
Dahlias? from Hernandez
There are plenty of narratives which say that Aztecs cultivated dahlias for medicine and food as well as ornamental purposes, but, as Martin Král points out, there is actually little evidence to support this. Instead our first real account of the dahlia, and apparently an image of one, comes from a manuscript compiled by one of Philip II’s physicians, Francisco Hernandez, who was sent to the new colonies in the Americas in 1570 to compile a report on their natural history. He returned to Spain in 1577 with at least 16 folio volumes but died the following year before his work was printed.
His manuscript sat on the shelf in the royal library gathering dust until 1615 when some parts were published [in Spanish and unillustrated.] More followed, this time in Latin with with images, in 1651. Unfortunately the manuscript and its illustrations were “rearranged” for publication, and got a bit mixed up. The result is that it’s at least possible that the plant shown isn’t a dahlia at all but of a related plant family such as bidens, coreopsis, or cosmos. Unfortunately we can’t check back with the original manuscript since it was destroyed in a fire.
One thing does appear clear and also surprising. There are no records of dahlias in Europe until the very end of the 18thc. If it’s so common in its native territory why not? The fact it wasn’t included in the flood of plants that were imported to Europe in the 16th and 17thc suggests that it wasn’t actually seen as important or useful and possible not even very attractive. It’s only when botany starts investigating less obviously interesting plants for their own sake that this ‘weed’ finally reaches Europe.
Dahlia pinnata Cav.
from Icones et descriptiones plantarum, vol. 1: t. 80 (1791)
In 1786 a Spanish botanical expedition was sent to Mexico to complete Hernandez’s work on natural history [only 200 years later – talk about manana!] and sent back parcels of seeds and other plant material to Spain. Dahlia seed was included in one of these and must have reached Madrid before 1789.
Dahlia pinnata Cav. [as Dahlia rosea]
from Icones et descriptiones plantarum, vol. 3 (1794)
Antonio José Cavanilles (1745-1804) at the Royal Botanical Garden of Madrid, photo by Marc Ryckaert
Cavanilles was a correspondent of Carl Peter Thunberg, the globe trotting pupil of Linnaeus and it was in honour of one of Thunberg’s acquaintances, the Swedish botanist Anders Dahl who had just died that Cavanilles named the new discovery: Dahlia pinnata. Later volumes of Icones included what Cavanilles thought were 2 more species : Dahlia rosea and Dahlia coccinea.
Dahlia pinnata Cav. [as Dahlia purpurea
from Herbier général de l’amateur, vol. 5: (1817-1827)
Like all good plantsmen Cavanilles was anxious to spread the word about these new plants he had described and was growing in Madrid. In 1802 he sent some seeds and tubers of all three species to another of his correspondents, André Thouin at the Jardin des Plantes in Paris. Thouin succeeded in growing them and in turn distributed seeds and tubers to other gardeners he knew. After his experience growing them he wrote that Cavanilles was mistaken and that there were only 2 species [arguing that D rosea and D coccinea were basically the same] but they had already hybridized and produced a great number of varieties with potential for more.
Dahlia pinnata Cav. [as Dahlia rosea ]
Allgemeines teutsches Garten-Magazin vol. 1: (1804)
Dahlia rosea Cav, by Pierre-Joseph Redouté Museum of Natural History, Paris
undated but early 19thc
On his return Bonpland was taken under the wing of the Empress Josephine and worked for her at Malmaison where he presumbaly gave seed to the director of all the imperial gardens, Count Lelieur de Ville‐sur‐Arce. While there is no record of Bonpland growing or selecting dahlias at Malmaison the count certainly did at another palace, St Cloud on the outskirts of Paris. There is an account of the gardens at St Cloud in 1818 by Joseph Sabine, secretary of the Horticultural Society of London, which talks of dahlias in shades of purples, dark and cherry reds, buffs, and even pale yellows, as well as striped ones and and the count is also thought to be the first to produce a fully double dahlia.
Dahlia pinnata Cav.
from The new botanic garden, vol. 1: t. 19* (1812)
One of the recipients of Humboldt’s largesse was Montpellier Botanic Gardens where the director Augustin de Candolle was already growing dahlias from seed given to him by Cavanilles. Now Candolle had new opportunities to expand his hybridizing experiments, and this led him to comprehend the taxonomic problems of dahlias. [Lucky man!] Because dahlias cross-pollinate easily and new colours and forms appear it became a real challenge to link these back to the original species. Candolle tried to tackle this in Note sur les Georgina published in 1810 in the Annals of the French Natural History Museum.
Mmmm I can hear you thinking why didn’t he call his article: Note sur les Dahlias?
Carl Ludwig Willdenow (1765-1812). ca. 1810.
That’s down to someone else who received seeds or tubers from Cavanilles: the Director of Berlin’s Botanic Garden, Carl Ludwig Willdenow who was also a great friend of Humboldt.
NOW.. if you want to get confused read the next few small print paragraphs about dahlia taxonomy- and if you don’t just skip to the next sentence in bold type
Willdenow knew that Cavanilles had named the plants after Dahl In 1804 BUT he also knew that in 1792 Thunberg had also named another plant –Dahlia crinita, a kind of witch hazel from South Africa – after Dahl because curliness of the flowers reminded him of his friend’s unruly hair.
The rules of botanical nomenclature mean that precedence is given to the name used in the first published description and it appears that Willdenow did not know that Cavanilles had already published his description in Icones in 1791. So to Willdenow the name Dahlia was already taken by the South African plant, [rather than the other way around] and therefore if he published a description he could ‘rename’ the plant himself. And that’s what he did. He honoured a friend from his student days, Gottlieb Georgi and called the plant Georgina
Next Willdenow re-described Cavanilles three species. He renamed D. coccinea Georgina coccinea. and then combined D. pinnata and D. rosea under the name Georgina variabilis. He chose “variabilis” because he’d realise that these plants were self-incompatible, and required out-crossing to produce seed, and that meant considerable and unpredictable variation in the next generation.
In the same year, 1804, Thouin in Paris also pictured and described three plants, but he called them D. pinnata, D rosea, and D. purpurea. In 1808 the English botanist Richard Salisbury listed and described four species, using D. sambucifolia instead of D. pinnata and D. bidentifolia instead of D. coccinea. [Are you still awake?]
Then in 1809 Willdenow revised his original description to include varieties of his umbrella species Georgina variabilis. A year later in 1810 he accepted his mistake and switched the plants back from Georgina to Dahlia. In 1810 William Aiton at Kew renamed D. pinnata and D. rosea as Dahlia superflua, and D. coccinea as D. frustanea, both of which alterations were then corroborated by DeCandolle and the editors of Curtis’ Botanical Magazine in 1817 as the only species in the genus. [Still following the plot?]
BUT matters were complicated by the rapid “discovery” of supposedly new species. By the year 1829 no less than 22 different species has been described before most were later merged by De Candolle who settled these disputes eventually by formally describing D. variabilis, D. coccinea, and D. cervantessii in 1836, and his decision remained uncontested for 43 years.
[Info for this section derived from Stanford University’s Dahlia Project which looks at floral morphology through genetics.]
So… eventually the name Dahlia variabilis was an obvious choice to describe an extremely variable group of plants and flowers, which are the progenitors of modern day hybrids.
So how and when did dahlias reach Britain? It’s traditionally thought to have been the work of two aristocratic women. The second edition of Hortus Kewensis records that seed was sent to Kew in 1798 by the Marchioness of Bute, wife of the British ambassador to Spain. Just to confuse things the first edition has 1789 but this was a printer’s error although for a long time people thought dahlias were here before they had been grown in Spain. But in any case it doesn’t matter becasue it seems the plants didn’t survive anyway.
Lady Elizabeth Webster, soon to be Lady Holland, 1795
Lady Holland was more successful. She was the colourful society hostess, who had made Holland House, in Kensington into one of the most brilliant centres of political and literary society in all Europe. She and her husband were in Spain and in 1804, she too was given either dahlia tubers or seeds or roots by Cavanilles. These were sent back to Holland House and included all three species he had described. All flowered later that summer. We know all this because the librarian at Holland House, Mr Buonaiuti, kept up a running correspondence with Lord Holland. By July 1806, he wrote that “above a hundred plants of Dahlias are now growing in various parts of the gardens at Holland‐House in the highest luxuriance.” New dahlias continued to arrive in Kensington and probably included some from France and Germany, and from there seeds soon were distributed to other British estates and crucially to commercial nurseries.
Dahlia pinnata Cav. var. atro-sanguinea [as Georgina variabilis ]
from Hortus sempervirens, vol. 60(1825)
In 1824 Lord Holland wrote a verse for his wife:
The dahlia you brought to our isle
Your praises forever shall speak
‘Mid gardens as sweet as your smile
And colour as bright as your cheek
Dahlia coccinea Cav.
Curtis’s Botanical Magazine, t. 740-786, vol. 20: t. 762 (1804)
But in fact Lady Holland was not the first Briton to grow dahlias. She was beaten to it by a well-travelled Scots plant hunter and nurseryman named John Fraser [of whom more in another post soon.] Not only had Fraser met Humboldt and Bonpland on their American odyssey but in 1802 he managed to obtain Dahlia coccinea probably from the Jardins des Plantes in Paris and grew it in his nursery near Sloane Square. It was included in Curtis’s Botanical Magazine in 1804 where it was also said to have flowered at Chelsea Physic Garden the previous year.
Dahlia pinnata Cav.
The Botanist’s Repository , vol. 6: t. 408 (1804-1805)
Dahlia pinnata nana, from Botanist’s Repository vol. 7
The Botanist’s Repository soon also included Dahlia pinnata and then a semi‐double variant, D. pinnata nana ‐which shows the variability of dahlias and/or their ease of hybridization.
Within a few years of their arrival the dahlia became widely available and quickly caught on as a fashionable flower all over western Europe. I’ll look at their later history [I hope less confusingly] in another post soon…
The Gardens Trust 
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‘Vulgar’ is more of an English word. It is not often used here, although most of us know what it means. It certainly works for dahlias. It seems to me that dahlias are more popular among the English too. My colleague down south refers to them as ‘dago sunflowers’, even though I have not grown them in many years, and they are really no more popular among ‘my people’ than among anyone else. An English lady who helped me with the Garden Report on KSCO was more interested in dahlias than I was.