The Science Behind Color Changing Dahlias

The Science Behind Color Changing Dahlias

Have you ever had a Dahlia that has seemingly changed color and wondered how that is even possible? The secret lies in the science behind these beautiful flowers. From genetics to the environment, discover the fascinating process that allows dahlias to change color before your very eyes.

Two main factors affect Dahlias and their color-changing ability. These factors can be neatly summarised as genetics and environment; let’s look a little deeper at both.

Dahlia Genetics

Dahlias are octoploids, meaning they have eight sets of chromosomes, whereas most living things are diploids and only have two sets, like humans. This gives us insight into how complex and unique the world of Dahlias can be. It is this sizeable genetic makeup that allows for a single flower species to be so diverse.

But how does having a lot of chromosomes mean Dahlias can change color? Let’s back things up a little and go right back to the start and take a look at the original, wild Dahlia.

Mexican Dahlias
Mexican Dahlias or Species Dahlias are quite different from modern varieties.

Above is a photo of a Mexican Dahlia, so named because they grow wild in Mexico and much of central America. This is the original Dahlia, and it is from the obsessive breeding of this flower that all modern varieties have been created.

You can see that they are quite different from a lot of modern Dahlias and more closely resemble Daisies than, say, a large cafe-au-lait Dahlia. This is no surprise, as Dahlias are members of the Asteraceae (daisy) family.

But over the years, Dahlia breeders have managed to selectively breed for particular genetics, such as more petals or larger blooms. As a result, your modern large show Dahlia has very little in common with the original flower.

Moreover, many of the traits we love about Dahlias are recessive and only occur very rarely. Given the chance, Dahlias love to have an open pollen center, a single set of petals, and a small pollen count. These are the traits the flower prefers, which is why Dahlias grown from seed often revert to these characteristics.

That is why Dahlias are commonly grown from tuber divisions and cuttings; this way, the plant is a clone of the parent, and there is no chance for any unfavorable genetics to return. This is how all the popular varieties of Dahlia are grown and continue to exist generation after generation.

How Genetics Can Lead to Color Change

This brings us to how genetics of Dahlias can lead to color change. The simple reason is that Dahlias are very genetically volatile. They are Frankenstein flowers that, while undoubtedly beautiful, would never exist in the real world without human intervention.

This unstable nature can lead to color change within the plant, they can be the perfect pink flower for many years, and then, seemingly out of nowhere, something triggers in the plant, and the next year they are a much deeper red.

While this is rare with single-colored Dahlias, it is actually much more common with the variegated type. It is easy to see why, as the plant already has two separate colors vying for dominance, and sometimes one color wins out.

Variegated Dahlia Blooms
Variegated Dahlia Blooms

Growing Conditions

If you have grown Dahlias for a while, you may have noticed that the growing conditions of your plants can affect the color of the flowers.

This is particularly true regarding Dahlias and the amount of sunlight they receive; generally, the more direct sunlight, the brighter and more vivid the bloom will be.

But why so? Well, the answer lies in how the flowers get their color in the first place, let’s take a deeper look at the science.

How Growing Conditions Can Lead to Color Change

The color of your Dahlias is based on the type of flavonoid present in the plant and some other related compounds.

Red dahlias, including oranges, pinks, magentas, etc., have a build-up of anthocyanin in various levels, which leads to different colors.

While yellow Dahlias get their color from the formation of deoxychalcones in the flower.

This involves growing conditions because flavonoid levels can be greatly affected by growing conditions, with the amount of sunlight, in particular, increasing the levels.

The higher the flavonoid levels in the petals, the brighter and more vivid the color. This explains why dahlias can seemingly change color depending on how much direct sunlight they get.

All of my information for this section was taken from this scientific paper; if you want to get into the weeds on this, I highly recommend giving it a read.


Why Are There No Blue Dahlias?

This is answered in the same paper that I linked above. I will provide their direct quote and explain it in layman’s terms.

Delphinidin derivatives are not formed due to the absence of flavonoid 3’,5’-hydroxylase in dahlia petals, which provides an explanation for the lack of blue dahlia flowers.

Delphinidin is the plant pigment responsible for blue hues in flowers, but it doesn’t form in Dahlias.

How Do I Make My Dahlias More Vibrant?

Dahlias are more vibrant the more sunlight they receive. So move poor-performing dahlias into a sunny spot to increase their color.

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