The dahlia reached Europe thanks partly to a spy sent to steal dye bugs
Dahlias come in nearly every colour except blue, from 5-centimetre buttons to dinner plates a foot across. That dazzling range comes from genetics: garden dahlias carry eight sets of chromosomes. Their route from Aztec gardens to Europe involved a royal physician, a French botanist hunting cochineal insects and a Madrid garden director.
Dahlia is a genus of 49 species of bushy, tuberous perennials native to Mexico and Central America, in the daisy family alongside sunflowers and zinnias. What looks like a single bloom is a head of many small florets, each a flower in itself. Stems run from 30 centimetres to over 2 metres, and most flowers have no scent, which fits the pattern of plants that lure pollinators with colour instead. Their variety owes much to being octoploid and to abundant transposons, mobile stretches of DNA that shuffle genes around. The tubers store energy as inulin, a fructose polymer, rather than starch, and indigenous peoples gathered and farmed them for food.
Spaniards noted the plants in Mexico in 1525, but the first real description came from Francisco Hernández, physician to Philip II, sent in 1570 to survey the colony's natural products. He recorded names used by Aztecs and Toltecs that translate roughly as water cane or hollow-stem flower, after the plant's hollow stalks. His companion Francisco Domínguez drew plants with strikingly double blooms.
The European story really begins in 1787, when the French botanist Nicolas-Joseph Thiéry de Menonville, in Mexico to smuggle out the cochineal insect prized for scarlet dye, reported odd, beautiful flowers in an Oaxaca garden. In 1789 Vicente Cervantes of the Mexico City botanical garden sent plant material to Antonio José Cavanilles in Madrid, who flowered it and in 1791 named the genus after the Swedish botanist Anders Dahl. Seeds and tubers soon spread to Italy, Germany, France and Kew, where an early batch sent by the Marchioness of Bute flowered but died out within a few years.
Alexander von Humboldt sent more seed from Mexico in 1805, and crosses between his stock and the Madrid plants produced a flood of new forms; in 1829 European growers lumped everything under one name, D. variabilis, which botanists do not accept. Classification remains messy. The garden dahlia turned out to be a hybrid form of Dahlia sorensenii, and only one of the traditional sections holds up genetically.
Source: Dahlia
