Mystery of Black Dahlias: A Breeder’s Guide to Creating Rare Colors

Copyright © 2025 by Steve K. Lloyd
All Rights Reserved

Can a dahlia be truly black? Is it possible for such striking hues to be deliberately bred? And what secrets lie behind their shadowy brilliance?

Black dahlias have long fascinated gardeners and artists—and occasionally lent their name to darker cultural stories. Though no dahlia is truly black, a handful of varieties appear near-black to the eye, displaying the deepest maroon, plum, and chocolate tones imaginable. These extraordinary blooms stand out in the garden, commanding attention with their dramatic presence.

Thanks to a handful of scientific studies published in recent years, we now have a clearer understanding of how dark pigmentation forms in dahlias—and how breeders might harness these colors in their own hybridized creations.

My goal is to make the path to creating dark-pigmented dahlias more understandable—without losing readers in the weeds of technical jargon.

The petals of so-called black dahlias are actually deep shades of red, purple, or crimson—so saturated that they read as black to the eye.

This optical illusion is created by high concentrations of anthocyanins, a group of pigments found in many plants. Anthocyanins are responsible for the blues, reds, and purples in everything from blueberries to pansies. The darker the bloom, the more densely anthocyanins are packed into its petals.

Unlike pigments such as melanin in animals or certain unusual plant pigments like the ones found in beets, anthocyanins are derived from the flavonoid pathway—a common set of biochemical steps shared by many flowering plants

The specific hue a dahlia displays depends on which anthocyanins are produced, in what amounts, and how they interact with other cellular factors such as pH, a measure of acidity.

Most black dahlias don’t contain new or exotic anthocyanins. What sets them apart is either the sheer amount of pigment they produce, or a reduction in competing pigments that would otherwise lighten the bloom.

While anthocyanins contribute the red-to-blue spectrum, yellow pigments come from a different group of plant compounds called chalcones and flavones. These are part of a broader pigment family known as flavonoids. 

If any of these terms are unfamiliar (as they were to me when I began researching this article), each will be explained in context, and a glossary is available at the end for easy reference.

Each dahlia bloom owes its color to a blend of naturally occurring pigments, layered in precise and surprising ways. While anthocyanins are responsible for red, purple, and blue tones, yellow pigmentation comes from compounds called chalcones and flavones. These yellow pigments act as visual “lighteners,” and when they’re absent, dark tones appear more intense.

Most blooms are shaped by a dynamic balance between multiple pigment types, and the overall coloration we see depends on how these pigments combine and how strongly each one is expressed. In a bloom where dark pigments dominate—without interference from yellow or pastel tones that would normally soften or lighten the effect—the result can appear nearly black to the human eye.

This pigment balance is controlled by a web of biochemical reactions—a sort of assembly line that transforms raw molecular building blocks into finished pigments. Scientists call this a biosynthetic pathway. You can picture it as a branching flowchart, where each stage is guided by enzymes.

These enzymes act like guides, steering reactions along different chemical routes. The route they take determines which pigments will ultimately be produced—red, yellow, orange, or a deep, moody purple.

Every enzyme mentioned so far is made by a specific gene. If the gene is active, the enzyme gets made and pigment production proceeds. If the gene is suppressed or disrupted, pigment output changes—sometimes dramatically.

One important example is the enzyme flavone synthase II (FNS II). This enzyme helps create yellow pigments in many dahlia cultivars. When FNS II is missing or less active, yellow pigment production drops—leaving the door open for darker tones to dominate.

Another key player is chalcone reductase (CHR), which nudges pigment production toward a unique set of yellow compounds known as 6’-deoxychalcones. These pigments give some dahlias their warm yellow or orange glow. But when CHR is suppressed, the pigment profile can shift, deepening the bloom's overall tone.

Gene activity can also be influenced by regulatory genes—like DvIVS, which acts as a master switch for anthocyanin production. When this gene is turned up, deep reds and purples can intensify. When it’s turned down or interrupted, color expression may weaken or change.

Sometimes, the darkest flowers in the garden aren’t entirely healthy. Several growers have noted that certain unusually dark cultivars—like Czarny Charakter (often shortened to Czarny)—appear to show signs of viral infection, particularly Tomato Spotted Wilt Virus (TSWV) or Tobacco Streak Virus (TSV).

The name Czarny Charakter comes from Polish and translates roughly as “villain” or “dark character,” a term often used in literature to describe an antagonist. It's a fitting name for a flower that captivates with beauty but raises questions about what lies beneath.

Viruses can interfere with pigment production, sometimes suppressing yellow pigments and unintentionally mimicking the visual profile of a “black” dahlia. In such cases, the coloration may be the result of metabolic disruption rather than stable genetics.

One study found that TSV (strain dahlia) can suppress the gene expression of FNS II in infected plants, directly leading to reduced yellow pigment synthesis. 

The study included observations of the variety Fidalgo Blacky, which retained its dark coloration even when infected—a trait not shared by many other cultivars in the trial. This stability suggests that in some cases, deep pigmentation can be genuine rather than virus-induced.

Fidalgo Blacky was introduced in 1993 by Richard and Patty Matthies , Washington State hybridizers whose 52 ADS-registered dahlia varieties are all named for Fidalgo Island, coincidentally the place where I live and grow dahlias.

The series began with Fidalgo Frills and Fidalgo Olympus in 1966, and concluded with Fidalgo Goblin in 2000.

Today, fewer than a dozen of Matthies’s varieties are still readily available for sale. I am growing Fidalgo Blacky in my garden for the first time this year.

Cool night temperatures may slow the degradation of pigments, helping preserve dark tones. Conversely, heat stress and nutrient imbalances can cause irregular coloration or fading. This may help explain why so many prolific dahlia breeders are based in the cool, temperate growing zones of the Pacific Northwest, where harsh heat is rare and summer daylight is abundant.

Observations like these are echoed in research, though sometimes with unexpected nuance—especially when it comes to how yellow pigments respond to cooler conditions.

One study from Japan showed that in certain yellow dahlias—specifically Gold Crown and Kamakura cultivars—low-temperature conditions increased the expression of flavone-related genes. In these cases, the cooler weather enhanced yellow pigments at the expense of darker tones.

That means a variety like Fidalgo Knight or Arabian Night might bloom nearly black late in the growing season, but show more burgundy tones when grown in midsummer heat. This observation is supported by my own photos, which show striking color differences in these varieties from July and August to September, when the days have grown shorter and much cooler in my Pacific Northwest 8b growing zone.

Dahlia ‘Fidalgo Knight’ in the author’s garden on August 15. Photo by Steve Lloyd.

Dahlia ‘Fidalgo Knight’ in the author’s garden on September 23. Photo by Steve Lloyd.

Dahlia ‘Arabian Night’ in the author’s garden on July 24. Photo by Steve Lloyd.

Dahlia ‘Arabian Night’ in the author’s garden on September 21. Photo by Steve Lloyd.

If you want to breed for darker blooms, begin by choosing parent plants that already exhibit rich, saturated color.

Selecting parents with minimal yellow or peach tones increases the likelihood that darker offspring will emerge.

The surest path to deeper coloration is through line breeding: crossing dark types with each other over several generations to reinforce the trait.

Dahlia ‘Czarny Charakter’. Photo credit Chumlee Cangiamillla. Used by Permission.

Dahlia ‘Czarny Charakter’. Photo credit William Evans. Used by Permission.

Tracking results is essential. Even if you're not sure why a particular seedling turned out so dark (or so disappointing), keeping good records allows you to spot patterns over time. 

This data becomes more valuable than any single cross—and often reveals hidden potential in your seedling beds.

Some dahlia breeders also watch foliage color as a secondary trait. Just as petals derive their coloration from anthocyanins, so too can stems and leaves.

Seedlings with dark or burgundy foliage may indicate high anthocyanin potential overall.

While this article focuses on flower color, a related pursuit is underway in my own breeding efforts: the development of seed-grown dahlias with dark foliage.

Just as dahlia blooms derive their coloration from anthocyanins, so too can stems and leaves.

Selecting for this trait is trickier than it sounds. Some seedlings that emerge with burgundy-tinged foliage will green out as they mature. Others retain their dusky hue all season, and actually become darker under the mid-summer sun.

My goal is to isolate those few black-leafed dahlias that hold their foliage color reliably, and incrementally work toward bloom forms other than singles, in colors besides the most-common reds, yellows and oranges.

Imagine a dahlia with dark, almost black foliage and a near-black, fully double bloom similar to Czarny Charakter or Fidalgo Blacky. Or how about a white ball resembling Blizzard, but with leaves the deep shade of David Howard or one of Dr. Keith Hammett’s Mystic series dahlias?

It’s a slow process, but one I find deeply satisfying. Stay tuned for updates!

• Anthocyanins – Pigments that produce red, purple, and blue colors in plants.
  
  

• Biosynthetic pathway – A sequence of chemical reactions in plants that builds complex compounds like pigments from simpler ones.
  
  

• Chalcones – Yellow pigment precursors formed early in the flavonoid pathway.
  
  

• Chalcone reductase (CHR) – An enzyme that shifts pigment production toward orange and golden yellow tones.
  
  

• DvIVS – A regulatory gene that turns anthocyanin pigment production on or off.
  
  

• FNS II (Flavone Synthase II) – An enzyme that helps form flavones, which contribute to yellow coloration.
  
  

• Flavonoid pathway – A complex chain of reactions in plants that creates anthocyanins, flavones, chalcones, and other pigments.
  
  

• Line breeding – Repeatedly crossing similar individuals (e.g., dark-flowered dahlias) to reinforce a trait across generations.
  
  

• Post-transcriptional gene silencing – A process where cells suppress certain genes after their RNA has been made, often used in virus defense.
  
  

• Transcriptome – The full set of RNA molecules a plant produces under certain conditions—used to study gene expression.
  
  

Deguchi, A., Tatsuzawa, F., Hosokawa, M., Doi, M. and Ohno, S. (2016). Quantitative evaluation of the contribution of four major anthocyanins to black flower coloring of dahlia petals . The Horticulture Journal, 85(4), pp.340–350.

Deguchi, A., Tatsuzawa, F., Hosokawa, M., Doi, M. and Ohno, S. (2015). Tobacco streak virus (strain dahlia) suppresses post-transcriptional gene silencing of flavone synthase II in black dahlia cultivars and causes a drastic flower color change . Planta, 242, pp.663–675.

Halbwirth, H., Muster, G. and Stich, K. (2008).  Unraveling the biochemical base of dahlia flower coloration . Natural Product Communications, 3(8), p.1934578X0800300807.

Muthamia, E.K., Naito, K., Okada, H., Karasawa, Y., Kikumura, T., Nara, T., Hamauzu, Y., Motoki, K., Yasuba, K.I., Yoshida, Y. and Kitamura, Y. (2024). Elucidation of low-temperature regulated flavone synthesis in Dahlia variabilis and its effects on flower color . The Horticulture Journal, 93(4), pp.335–343.

Ohno, S., Yokota, M., Yamada, H., Tatsuzawa, F. and Doi, M. (2021). Identification of chalcones and their contribution to yellow coloration in dahlia (Dahlia variabilis) ray florets . The Horticulture Journal, 90(4), pp.450–459.

Ohno, S., Yamada, H., Maruyama, K., Deguchi, A., Kato, Y., Yokota, M., Tatsuzawa, F., Hosokawa, M. and Doi, M. (2022). Identification of a novel chalcone reductase gene for isoliquiritigenin biosynthesis in dahlia (Dahlia variabilis) . bioRxiv.

Thill, J., Miosic, S., Ahmed, R., Schlangen, K., Muster, G., Stich, K. and Halbwirth, H. (2012). ‘Le Rouge et le Noir’: A decline in flavone formation correlates with the rare color of black dahlia (Dahlia variabilis hort.) flowers . BMC Plant Biology, 12, pp.1–14.

This article was developed through a close collaboration between the author (a dahlia hybridizer and educator) and an AI language model trained on a large corpus of scientific and botanical texts. The author selected, reviewed, and uploaded all cited studies, and carefully reviewed the article at each stage to ensure factual accuracy, clarity, and accessibility. The AI assisted in summarizing technical material, proposing structure, and refining language. All final edits and interpretations reflect the author's expertise and voice.