Dahlias are incredibly diverse, and most of the time that’s a good thing — but not always. Unlike most living things which have two sets of chromosomes, dahlias are octoploids which means they have eight. This wider range of genetic possibilities is the source of their astonishing diversity, but it also creates more opportunities for things to go awry.
Chimeras — named for a mythological beast that was part lion, goat, and snake — are plants in which cells of two different genetic make-ups exist side by side. Many bi-tone, speckled, and other variegated dahlias are chimeras, and the interaction between their genetically different sections or layers is often unstable.
‘Nonette’, for example, is usually an apricot colored dahlia sprinkled with tiny bits of red, but sometimes one or more of its flowers are all apricot or all red. (See photos of this and more at our Wacky Dahlias page.) Most of the time most flowers of a chimera are normal with only a random few being different, but sometimes the entire plant changes so that all of its flowers are different, and sometimes only one section of an individual flower goes wacky.
Growing conditions can make a difference, too. Flower colors often change as the weather cools and sunlight diminishes in the fall, and stressful conditions — too much heat or not enough water, sunlight, or nutrients — can sometimes make double flowers bloom with fewer petals.
Most of these changes are only temporary (and often entertaining), but if you have a dahlia that bloomed all wrong this year, please let us know so we can send you a refund, credit, or replacement. And if you have a photo of one of our dahlias gone wacky in your garden, we’d love to see it!