Up at the Tree House…Orchard Bees!

Conservation // April 27, 2022

With each consecutive warm day, nature awakens and spring announces its arrival. One of my favorite “early risers” of the season are mason bees (Osmia lignaria). Also called orchard bees, they are vital to the Tree House’s Food Forest fruit production, which should begin this year.

Mason bees emerge with the early blooms and can pollinate them when other pollinators have yet to emerge. Mason bees are just one of over 400 native bee species in Pennsylvania, which include bumble and carpenter bees. Too often, the non-native, domesticated European honeybee is the face of the Save the Bees movement. Although they are pollinators, bees are just one small part of a team of pollinators that are crucial to food systems, and the ecosystem as a whole.

Unlike the honeybee, most of our native bees are solitary. Individual queens work to gather nectar and pollen to feed their larvae in their mostly underground nests, or nests in existing holes. You may see them nesting close to each other, but they are working solely on their own nests. While honeybees have an important niche in agriculture as hives are managed for honey and other products, when it comes to pollination, native bees, such as mason bees, are significantly more efficient pollinators. Mason bees collect pollen and nectar to eat, but they do not store them as part of a community.

They also have a smaller foraging range, so they can use their efficiency to pollinate more plants in a specific area, like a managed orchard. Mason bees do not have a corbicula, or pollen pocket, on their back legs to hold their collection, and are instead covered with hairs that capture pollen as they plow into flowers with little grace. Covered in pollen, they visit a variety of flowers, including fruit trees, in the early spring. Because the bee is carrying more pollen freely on its body, the exchange rate inside the flowers is greater.

Fusae Yeshareem shows off the bee house she made in 2021. Photo Credit: Christina Mores

In another efficient practice, the mason bees utilize existing holes for their nests, making it easier to build and manage houses for them. Last spring at the Tree House, we created basic mason bee houses to place in the orchard and hosted a building workshop. Both the workshop and the nests were successful for all. Our houses and some of our learner’s houses were used by mason bees.

How did we know these were mason bee nests? A mason bee gets its name from using clay soil to fill in the gaps between the egg chambers it makes in a hole and to seal the end. In a hole or a tube, as in many man-made houses, the mason bee queen will seal the back with clay, deposit pollen with an egg, then create a thin clay wall, before continuing the process through the tube. Inside, the egg will hatch, and the larva will grow throughout the spring and summer. In late summer, the mason bee will spin a silk cocoon in which it will go through complete metamorphosis. The bees overwinter as fully formed adults and emerge from the tube in early spring, males first (laid in the front of the tubes) and then the females.

After mating, the queen bees begin the cycle again. As I dive deeper into native bee management, the Wissahickon Environmental Center will be adding more houses to the Food Forest and workshops to the calendar to further encourage nesting by the native bees in our orchard and to support neighbors doing the same at their homes. These workshops will cover building, management, native bees, native plants, and habitat creation for all.  In the future, we hope to also make the workshops available online.

Christina Moresi, M.Ed., is an
Environmental Education Planner at the
Wissahickon Environmental Center