Not all flowers attract bees. While bees are highly effective pollinators, the plant kingdom is diverse, and many species have evolved unique strategies for pollen transfer. This specialization is the result of co-evolution, where flowers and their most effective partners have developed traits that perfectly match one another.
The Primary Attraction Mechanisms
Flowers that rely on bees have developed specific mechanisms to ensure a visit. These features serve as clear signals, guiding the insects directly to the reproductive structures. The visual appeal often includes nectar guides, which are patterns on the petals frequently only visible under ultraviolet (UV) light. These UV patterns act like landing strips, directing the bee toward the flower’s center where the reward is located.
Beyond sight, flowers emit specific chemical signals, or scents, that bees detect from a distance with their sensitive antennae. These fragrances often signal a high-energy reward, such as sweet, herbal, or spicy aromas, indicating nectar is present. The physical structure of the flower is also adapted for bee visitation, providing a stable landing platform. Many bee-pollinated flowers have open faces or sturdy petals that allow the insect to land easily and access the reward of nectar and pollen.
Flowers That Bees Ignore
Many flowers have evolved to bypass bee pollination entirely, relying on alternative strategies for reproduction. Wind-pollinated plants, or anemophilous species, are a prime example of flowers that bees ignore. These plants, which include many grasses, oaks, and pines, do not need to advertise to animals. They typically lack bright colors, strong scents, or nectar, instead producing vast quantities of lightweight pollen carried by air currents. The absence of these standard floral advertisements means there is no incentive for a bee to visit.
Other flowers are highly specialized for different animal pollinators, such as hummingbirds, moths, or bats. Flowers adapted for hummingbirds, like the Cardinal Flower, are often bright red and have a long, tubular shape. This structure accommodates a hummingbird’s long beak, but the nectar is too deep for most bees to reach. Furthermore, red is a color that bees cannot see well, making these flowers visually unappealing. Self-pollinating flowers also have little need for external visitors, often keeping their reproductive organs closed off or maturing them in a way that encourages self-fertilization.
How Bees Perceive the World
A bee’s sensory system dictates which flowers it can effectively pollinate. Bees possess trichromatic vision, meaning their eyes use three color receptors, but their spectrum is shifted compared to humans. They see blue, green, and ultraviolet (UV) light, which makes them highly sensitive to colors in the violet and blue range.
The bee’s inability to see red means that red flowers appear dark or green, blending into the foliage unless they also reflect UV light. Their UV sensitivity allows them to see the nectar guides that are completely invisible to the human eye. This specialized vision helps them quickly locate the pollen and nectar source within the bloom.
Bees also use chemoreception to navigate the flower landscape, detecting floral scents with specialized receptors. This sense allows them to identify flowers from a distance and determine the quality of the nectar and pollen reward. Finally, the bee’s physical size and proboscis length constrain its choices. A long-tongued bee can access the nectar in a deep, tubular flower, while a shorter-tongued bee is restricted to more open, accessible blooms.