Blooming prolifically from late summer until the first frosts, dahlias are the glamorous stars of the early autumn garden with their myriad colours and forms.
From the thousands of varieties trialled at Dyffryn in Wales in the early 1900s, to Agatha Christie’s collection, planted at Greenway in Devon during the 1950s (the flower even featured in one of her murder mysteries), we explore the dahlia’s fascinating horticultural history and its role in the creation of many of our gardens.
From Mexico to Europe
The myths around the history of dahlias are as complex and varied as the flowers themselves. Mexico’s national flower hails from the mountainous regions of Central America but the brilliantly-coloured blooms we covet today have come a long way from these native wild flowers.
In 1570, the scientist Francisco Hernández was sent to Mexico by King Phillip II of Spain to research the region’s natural history. Dahlias may have featured in his descriptions of over 3,000 plants then unknown to Europeans. But it wasn’t until the late 18th century, when botany was developing as a science, that dahlias were first cultivated in Europe. In 1786 a Spanish expedition returned to Mexico to complete Hernández’s work and dahlia seeds were among the plant material sent back to Madrid’s Royal Botanic Gardens.
It was here in 1789, that a botanist/priest named Antonio José Cavanilles began work on the collection. He published the first descriptions and drawings of three dahlia species, naming the new plants he raised after Andreas Dahl, a recently deceased Swedish botanist and pupil of Carl Linnaeus (the father of modern taxonomy). Seeds and tubers from these dahlias were widely dispersed to botanists and plant enthusiasts across Europe in the early 1800s.
The first dahlias raised in Europe were single, open-centred flowers but horticulturalists soon discovered that when grown from seed, dahlias naturally hybridise, readily changing their colours and shape. This caused a particular headache for plant taxonomists trying to keep up with naming new varieties. Double dahlias were first bred in Germany in 1808 and growers quickly began selecting for specific traits. By 1820 around 100 dahlia varieties had been cultivated; in just twenty years that number had risen to 2,000.
The Victorians loved dahlias with their exotic, richly-coloured blooms. When the Horticultural Society (later RHS) started regular flower shows in 1831, its September event was dedicated to dahlias. As they became the subject of serious competitions, the National Dahlia Society was set up in 1881. In the 1930s, at their peak of popularity, there were 14,000 named dahlia cultivars; over the last century, almost 50,000 varieties have been listed.
The thousands of dahlia cultivars are classified by their different flower forms. There are 14 classification groups, including ‘collarette’, ‘waterlily’, ‘single orchid’ (star) and ‘fimbriated.’
Dahlias at Dyffryn
When dahlias were trialled throughout the 19th century, the flowers were judged for their decorative qualities as specimens in the greenhouse or for floral arrangements.
Reginald Cory (1871-1934) the wealthy owner of Dyffryn near Cardiff changed all that. A keen horticulturalist and sponsor of plant collecting expeditions, he began the first trials of dahlias as garden plants in 1913, turning over most of his garden beds to thousands of different dahlias. These were judged by a joint committee of the National Dahlia Society and the RHS.
After the First World War dahlia trials resumed and in 1923 Reginald sponsored the RHS Cory Cup for Dahlias. It continues today as a memorial cup awarded to the grower of the best hardy plant of garden origin.
Given Reginald Cory’s knowledge of plants and his passion for the unusual and rare, it’s easy to see how dahlias captured his imagination. Dahlias can be found across different areas of the gardens at Dyffryn today. The modern collection features all 14 flower classifications as well as several of the species, including the giant tree dahlia, Dahlia imperialis.
" Dahlias are central to the history of Dyffryn gardens and Reginal Cory's sunken Dahlia Garden will eventually be restored."
Agatha Christie's dahlias
Novelist Agatha Christie designed and planted a dahlia border at her holiday home Greenway on the English Riviera in Devon. She and her family spent late summer days here, just as the dahlias were beginning to bloom. Many of Agatha's original dahlia choices from the 1950s are still grown. The border sits in front of the putting green, where competitive games of Clock Golf were played.
Agatha even managed to weave the dahlia into one of her classic murder mysteries featuring her eponymous detective Miss Marple. In her short story, The Four Suspects, Miss Marple's knowledge of horticulture leads her to recognise some familiar dahlia cultivar names that appear in a riddle. The first letter of each name spells out the acronym DEATH and she's quickly able to name the murderer.
After over a hundred years of intense breeding, the last decades of the 20th century saw a decline in dahlias. Their popularity dwindled as gardening tastes changed. By the early 1980s, only around 20% of the thousands of dahlia varieties that had been available in the 1950s were still being cultivated.
Fortunately, the cyclical world of fashion has come full circle again. Christopher Lloyd's Exotic Garden at Great Dixter, created in the mid 1990s, the National Dahlia Collection founded by David Brown and the restoration of many dahlia gardens and borders by the National Trust have contributed to dahlias being in vogue once more. They can be found in dedicated gardens, mixed borders, bedding and container planting in many of our gardens. Here's our pick of some of the best places to see dahlia displays this autumn.