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April 4, 2023
We typically associate vivid imagery of brightly-colored native flowers in full bloom with pollinator habitat important to bees. But before the profusion of sun-drenched summer blooms, what floral resources does the landscape offer?
Spring ephemeral woodland wildflowers, completing much of their growth cycle before shade from the canopy limits photosynthesis on the forest floor, offer some of the first sips of nectar and grains of pollen to early emerging insects. It is prime time to get out into the woods and admire these fleeting beauties.
Bumblebees and other long-tongued bees are attracted to ephemerals such as Virginia bluebells (Mertensia virginica). They are also one of the few insects that can reach the nectar in the uniquely-shaped spur petals of Dutchman’s breeches (Dicentra cucullaria).
Various types of bees, including honey bees, bumblebees, carpenter bees, mason bees, cuckoo bees, Halictid bees, and specialist miner bees, visit the diminutive blooms of spring beauty (Claytonia virginica) to collect pollen provisions for developing offspring, some aiding pollination in the process. Contrasting pink stripes on the flower petals guide a bee to find its nectar reward. These ephemerals, among many others, are typically found as part of healthy forested ecosystems. Which brings us to trees!
Photo credit: Emily Broich
Most conifers, and some broadleaved trees – oaks, birches, aspens, elms, and walnuts among them, are wind pollinated. They share a reliance on wind pollination with a few of our major agricultural grain crops, such as corn, wheat, barley, oats, and rice, and do not invest resources to attract insect pollinators.
However, several early-blooming tree species are unassuming powerhouses for non-native honeybees and native bee pollinators alike. Orchardists and beekeepers have long keyed into this floral bounty. A single mature tree can produce thousands of blossoms, effectively maximizing resource density available to these pollinators in the vertical ecological space. Research suggests that bees will favor tree foraging, even in areas dominated by open land. This is important in terms of efficiency.
Many bees exhibit flower constancy, the tendency to restrict visits to a specific species of flowering plant on a given foraging trip, even if other rewarding species are also available. Although bees may miss out on a potentially better floral reward from time to time, this behavior is thought to help bees conserve energy while foraging. It also benefits the plant. While a bee focuses on the same floral target, it is more likely to spread pollen across plants of the same species, enhancing pollination, likelihood of seed development, and overall reproductive success.
Dozens of tree species and woody shrubs offer attractive floral foraging options to bees. Just a few among them:
Cellophane bee on male red maple flower (Photo credit: Heather Holmes).
Large, charismatic wildflower blooms might get more screen time than some of the early tree blooms that are harder to appreciate or photograph from eye level, but both are important to bee conservation for both generalist and specialist species. A diversity of floral resources, including native trees with prolific volumes of blooms, offers a succession of foraging opportunities throughout the season. If you want to help bees, don’t forget the trees.
Pennsylvania Green Infrastructure Projects Coordinator
Forests for the Bay