Blue flowers are indeed real, captivating observers with their unique coloration. These vibrant blooms emerge from complex biological processes within plants. Understanding how plants achieve these specific hues reveals insights into their cellular mechanisms and evolutionary adaptations.
How Flowers Create Blue
Plants primarily produce flower colors using pigments called anthocyanins. These water-soluble compounds are responsible for a wide spectrum of colors, including reds, purples, and blues. The specific shade of blue a flower displays depends on the type of anthocyanin, the pH level within the plant’s cells, and interaction with other molecules.
One key anthocyanin involved in blue coloration is delphinidin. While delphinidin itself can appear violet-purple, its transformation into a true blue hue is influenced by the pH of the cell sap in the flower’s petals. An alkaline environment can shift the color of anthocyanins, including delphinidin, towards blue.
Another mechanism for creating blue is co-pigmentation, where anthocyanins interact with other colorless or slightly yellow compounds, such as flavones or flavonols. These co-pigments form complexes with anthocyanins, stabilizing the blue color and deepening its intensity. Metal ions, like aluminum, can also chelate with anthocyanins and co-pigments to produce blue, as seen in hydrangeas. While less common for blue, structural color, which involves light interacting with microscopic physical structures rather than pigments, can also create blue appearances in nature, such as in some berries.
The Rarity of True Blue
Despite the existence of blue flowers, true blue remains relatively uncommon in the plant kingdom, appearing in less than 10% of flowering plant species. This rarity stems from the specific and complex biochemical conditions required for plants to synthesize and display a genuine blue pigment. Many flowers perceived as blue are actually shades of violet or purplish-blue.
Producing a true blue color requires the plant to create molecules that can absorb the red part of the light spectrum, which is challenging due to the high energy absorption needed. The evolutionary incentive for developing blue flowers relates to attracting specific pollinators, such as bees, which are highly sensitive to blue light. The interplay of anthocyanin types, precise pH levels, and the presence of co-pigments or metal ions makes true blue a chemically demanding color for plants to achieve naturally.
Naturally Blue Blooms
Several flower species naturally exhibit genuine blue hues. Forget-Me-Nots (Myosotis palustris) are well-known for their small blue blossoms, often featuring a yellow center. These tiny flowers are a classic symbol of remembrance.
Delphiniums are another example, producing tall spires of blue flowers. These perennials thrive in cooler climates and are appreciated for their vertical presence in gardens. Morning Glories (Ipomoea tricolor), particularly the ‘Heavenly Blue’ cultivar, display large, saucer-shaped blue flowers that unfurl in the morning light.
Hydrangeas (Hydrangea macrophylla) are influenced by soil pH for their blue color. In acidic soils, they absorb aluminum, which contributes to their blue coloration, while in more alkaline soils, they tend to be pink. Other blue blooms include Gentians, known for their blue trumpet-shaped flowers, and Cornflowers (Centaurea cyanus), with their distinct feathery blue petals.