Flower of the Week: Cornflower

The cornflower (Centaurea cyanus) is a fast-growing, lushly-blooming, herbal flower. This slender plant is highly ornamental when it blossoms in the summer and fall. It has a beautiful capitulum – an inflorescence surrounded by a circle of blue trumpet-like ray florets with serrate margin lobes.

Cornflowers are widely useful in horticulture, especially in newly-built gardens. Before other trees, shrubs, and persistent flowers mature to their best looks, this fast-growing country floret comes in handy to revive the dull color void of immature gardens.

From "Cornflower" to "Bachelor's Button"

Cornflowers originated in Europe, where they grow very well in almost all types of environments but especially in arable plain fields with fertile soil. In ancient times, Europeans often found them in the farmlands, thus the earthy name “cornflower”.

Cornflowers are great for flower arrangements. They remain vividly-colored when dried, and therefore are often used to make dried flowers. It’s said that bachelors in England like to pin them in their buttonholes to boost their courtship success rate, so the cornflower has earned an alternative name of “bachelor’s button”.

Dried cornflowers are edible. They can be served in salads for adornment. Cornflower petals are often added to Earl Grey tea as well.

A Famous Flower With a Long History

In Europe, the cornflower has a long history of cultivation and enjoys household fame. When tracing the genus name “Centaurea”, its written records easily date back to Ancient Greece. According to Pliny the Elder, Ancient Greeks used the name of the mythical Centaurs for these blue florets because they believed the story that Chiron, who mastered the art of healing, had used this plant to cure poisoning by the Hydra.

A Centaurs statue in the Tuileries Garden in Paris

Many regions, schools, organizations, and political parties in Europe also chose the cornflower to be their insignias. Today, it is the national flower of Estonia and Germany. Legend has it that cornflowers once helped Friedrich Wilhelm III of the Kingdom of Prussia and his family hide from Napoleon Bonaparte’s pursuing army. Since then, the cornflower has become the symbol of the Kingdom of Prussia, often appearing on the uniforms of high-ranking military officers.

The cornflower is often present in literature and art as well. The story of The Little Mermaid, by Hans Christian Anderson, begins with the words “Out in the ocean, where the water is as blue as the prettiest cornflower”, describing a beautiful, imaginary underwater world.

The Mesmerizing Blue

Of a cornflower’s most attractive features, nothing stands out more than its bright blue color. “Cyanus“, the specific epithet in its scientific name, simply means “blue”. In the field of design, “cornflower blue” is a unique color name, while in gemology, a higher-level color code of sapphire is also called the “cornflower” color.

In the 1910s, scientists extracted centaurocyanin, the same kind of anthocyanidin, from cornflowers and roses successively. But a cornflower looks blue, and a rose is red. Why the difference? Initially, people attributed it to the different pH values in the flowers’ fine structures, for like all other anthocyanidins, centaurocyanin looks red in an acid environment and blue in an alkaline one. However, later researchers realized the answer is far more complex.

Scientists in Japan discovered the ultimate answer as recently as 2005. The centaurocyanin in cornflowers doesn’t bear color by itself. Instead, 6 molecules of anthocyanidins and 6 molecules of flavones constitute an intricate complex protocyanin, with iron and magnesium ions contributing to its formation as well as extra calcium ions to keep it stabilized. It takes such a fully-formed complex to bestow that bright and rich blue upon cornflowers.

Can I Grow Cornflowers Well?

Cornflowers are perfect for country-style gardens, where they can scatter around and grow freely without much special care. Cornflowers require very little from their environments, flourishing naturally and tenaciously no matter whether the soil is barren or fertile, or the sunlight duration long or short. They can also be planted in flower beds or potted in just about any containers.

To create the most striking visual impact, it’s best to plant some other flowers among the cornflowers that share the same flowering season while differing vastly in color contrast, such as corn poppies, calendulas, etc. What’s more, the cornflower is an excellent nectariferous plant. For a rustic garden, they are the best choice to attract bees and butterflies.

A widely-grown garden plant, cornflowers are superbly capable of expanding. The plant has spread worldwide and naturalized nearly everywhere, including in North America and Australia. In some areas of the New World, it’s still considered dangerously invasive. Therefore, take careful measures to prevent its expansion when you grow it.

Interestingly and by contrast, wild cornflower distribution in Europe where the plant originated has reduced significantly due to intensive agriculture and herbicide overdosage.

Size: 30-70 cm tall, up to 1 m tall in fertile soil

Hardiness: USDA Hardiness Zone 2-11

Light duration: Full sun, partial shade tolerant

Soil: moist soil with good drainage, drought-tolerant once planted

Bloom time: Late spring through early summer