From our perspective as cornflowers (Centaurea cyanus), our most defining feature is our floral structure, which is exceptionally well-suited for attracting pollinators like bees and butterflies. Our flower heads are not single flowers but composite structures made up of numerous tiny florets. The outer ring features large, radiant, sterile ray florets that serve as visual landing platforms. Their bright blue hue is a high-frequency color signal easily detected by the trichromatic vision of bees. The true prize, however, lies in the inner disc florets. These tubular florets produce abundant and accessible nectar, a rich energy source. Their shallow, open shape presents no complex barriers, allowing a wide range of pollinators, from bees with shorter tongues to butterflies with their long proboscises, to easily access the reward we offer.
Beyond nectar, we provide a crucial protein-rich food source: pollen. Our anthers, the pollen-producing parts of the flower, are positioned prominently within the disc florets. We release our pollen in a gradual and deliberate manner, ensuring a sustained supply for visiting insects throughout our blooming period. For native bee species, including bumblebees and solitary bees, this pollen is vital for feeding their larvae. When a bee lands on our central disc, its movement vibrates the florets, efficiently dislodging pollen grains onto its body in a process known as "buzz pollination." This efficient transfer ensures the bee gets a good meal while simultaneously dusting it with pollen to be carried to the next cornflower, facilitating our cross-pollination needs.
Our value to the pollinator community is also defined by our timing. As annual plants, we are programmed to grow, flower, and set seed within a single season. In gardens across the US, we typically begin blooming in late spring and continue through the summer months. This flowering period is strategically vital. It provides a reliable food bridge between the early spring blooms of bulbs and fruit trees and the late summer abundance of coneflowers and asters. For butterflies embarking on their seasonal journeys and for bees provisioning nests during the peak of summer, our consistent and prolonged bloom offers a dependable pit stop, ensuring their energy needs are met when other resources may be scarce.
Our ability to attract these beneficial visitors is also a function of how we are grown. We thrive in full sun, which is also the preferred environment for most bees and butterflies who rely on solar warmth for activity. We are not particularly demanding regarding soil fertility, but we do require well-drained conditions. To maximize our attractiveness, we advise humans to plant us in generous drifts or clusters. A large patch of blue is a far stronger visual beacon than a single, isolated plant, making it efficient for pollinators to locate and forage from us. This grouping mimics our natural growth in meadows, creating a target-rich environment that supports greater pollinator diversity and activity within the garden ecosystem.
