Blue roses have long captured human imagination, often symbolizing mystery or the unattainable. Despite their allure, true blue roses, in the pure sense of a naturally occurring sky-blue bloom, do not exist in the natural world. This absence stems from specific genetic limitations within the rose plant itself. The shades of blue seen in roses are a result of either artificial treatments or advanced biotechnological interventions.
The Absence of Natural Blue
Roses naturally produce a range of vibrant colors such as red, pink, yellow, and various shades of purple, but a genuine blue is absent. This is due to the lack of the pigment delphinidin, responsible for blue coloration in many other flowers. Roses do not possess the flavonoid 3′,5′-hydroxylase (F3’5’H) gene, an enzyme essential for delphinidin biosynthesis. Instead, roses primarily synthesize anthocyanin pigments like cyanidin, which contributes to red and pink hues, and pelargonidin, which produces orange and red. Further complicating blue expression, rose petals maintain an acidic pH, which tends to shift any potential blue pigments towards a pinker shade.
How “Blue” Roses Are Made
As roses cannot naturally produce true blue, human ingenuity has stepped in to create what are commonly referred to as “blue” roses. One common method involves dyeing cut white roses. This process allows the cut stems to absorb blue dye dissolved in water, imparting a blue hue to the petals. This technique is effective for creating blue cut flowers, but it does not result in a living plant that naturally grows blue roses.
Genetic engineering offers a more advanced approach, introducing the missing blue pigment pathway into roses. In a breakthrough, Japanese company Suntory, in collaboration with Australian firm Florigene, engineered a rose to produce delphinidin. This was achieved by introducing the F3’5’H gene, sourced from pansies, into rose DNA, along with techniques to suppress the rose’s natural color-producing genes. The resulting ‘Suntory Blue Rose Applause’ was announced in 2004 and commercially launched in 2009.
Understanding “Blue” Rose Hues
The “blue” roses available display a spectrum of colors that are not a pure, vibrant blue. Artificially dyed roses can achieve a more intense blue, but this color is external and does not originate from the plant’s biological processes. Genetically engineered varieties, such as ‘Suntory Blue Rose Applause’, are more accurately described as lavender, pale mauve, or violet-blue.
While these engineered roses do produce delphinidin, the rose petal’s acidity can prevent the pigment from expressing a true blue. Some conventionally bred roses also exhibit strong purple or mauve tones, often mistakenly perceived as blue. Researchers continue to refine these methods, striving for a pure blue rose.