Irises (Iris spp.) are celebrated additions to gardens worldwide, known for their elaborate, ruffled blooms and striking colors. Their popularity has led to the cultivation of thousands of varieties, adding dramatic flair to spring and early summer landscapes. As awareness grows about declining insect populations, many gardeners want their plant choices to support local ecosystems, particularly by attracting bees. Understanding the specific relationship between the genus Iris and the insect world reveals a nuanced interaction that is far more specialized than a simple preference for nectar.
The Verdict on Bee Attraction to Irises
Whether bees like irises depends heavily on the specific iris species and the type of bee. Irises are visited and pollinated by various bees, but they are not universally high-value forage plants like clover or sunflowers. In Europe, for example, bumblebees (Bombus species) and solitary bees (Andrena species) are recognized as important pollinators for many wild irises. The effectiveness of a bee’s visit relates to its size and strength, which allows it to access the flower’s tightly guarded reproductive parts.
Smaller bees, such as the common honeybee (Apis mellifera), are often physically unable to maneuver into the correct position for pollination in many iris varieties. Observations show that larger, more robust bees are better equipped to navigate the floral structure and reach the nectar or pollen reward. Some iris species, particularly those in the Oncocyclus section, have evolved a unique relationship with specific solitary male bees (Eucera genus). These irises are nectar-less and instead offer the male bees a warm, protected overnight shelter, which facilitates pollen transfer. Other species, like Iris douglasiana, produce nectar, making them a more traditional target for foraging bees.
Structural Challenges of the Iris Flower
The unique anatomy of the iris flower presents physical challenges that make it a highly specialized target for pollinators. The flower is functionally divided into three distinct pollination units, often described as “gullets.” Each unit consists of a downward-curving outer petal, called the fall, which serves as a landing platform for the insect. Above the fall, the style crest arches over, creating a narrow tunnel leading toward the base of the flower. The anther, which holds the pollen, is positioned on the floor of this tunnel, while the receptive surface, the stigmatic lip, is located at the entrance, acting like a small, hinged flap.
For a bee to access the nectar reward, it must crawl deep into this tight space between the fall and the style crest. As the insect pushes forward, its upper thorax first brushes against the sticky stigmatic lip, potentially depositing pollen from a previous flower. Moving deeper, the insect’s back then contacts the anther, picking up a fresh load of pollen. This precise mechanism requires the pollinator to be a specific size—large enough to contact both the anther and stigma but small enough to fit into the gullet. For bearded irises, the prominent, fuzzy “beard” on the fall acts as a visual and tactile guide, directing the bee toward the narrow entrance of the pollination tunnel.
Maximizing Iris Pollination
Gardeners can encourage bee visitation to their irises by making intentional choices about variety selection and planting arrangement. Choosing iris varieties that have a more open or accessible structure can significantly increase the chances of successful bee visits. Dwarf iris species, such as Iris reticulata, are often cited as being bee-friendly, providing an early spring food source for emerging pollinators.
For bearded irises, selecting older or less highly bred cultivars may be beneficial, as some modern, highly ruffled varieties have floral structures that are too dense and intricate for easy bee access. Planting irises in large, dense groups, known as mass planting, creates a prominent floral display that is easier for bees to spot and investigate. Strategic companion planting can also draw bees into the vicinity of the irises. Positioning irises alongside other plants that are known to be strong bee attractants, such as herbs or flowers with exposed nectaries, increases the local pollinator traffic. The combination of a strong visual signal from mass planting and the proximity of high-forage plants improves the likelihood that a bee will enter the specialized iris blossom.
Alternative Pollinators for Irises
While bees are significant pollinators for many irises, they are not the only organisms responsible for the plant’s reproductive success. The diverse genus Iris has evolved to interact with a range of visitors, ensuring successful reproduction even when bee presence is limited. Hummingbirds are recognized as effective pollinators for certain North American species, such as the copper iris (Iris fulva) and Iris nelsonii. These birds probe for nectar at the base of the tepals, transferring pollen as they move between the flowers. Other insects, including long-tongued flies and specific types of beetles, are also known to interact with iris flowers. However, some visitors, like certain species of butterflies (Hesperiidae), may act as nectar robbers, consuming the flower’s reward without contacting the necessary reproductive parts to facilitate pollination.