Gardening: Protect bumblebees, the gentle giants in the garden
Recently my husband and I were cleaning up some broken concrete and rock. We had been working for a while when my husband noticed he was being pestered by some bumblebees. After looking around, we found several bees venturing in and out of some small holes in the rock pile. We’d found their ground nest, and it was time to back off and leave them be.
Bumblebees are our largest native bees and like many of our other natives are threatened by habitat loss and pesticides. Common Eastern Washington species include the red-belted bumblebee (B. rufocinctus), the Nevada bumblebee (B. nevadensis) and the yellow bumble bee (B. fervidus). There are 23 different bumblebees native to Washington. These lumbering giants of the garden come with a variety of yellow, rust and cream-colored markings but identification of specific bees can be a challenge.
These gentle bees are important pollinators in the garden especially for early plants because they fly at cooler temperatures than other bees. They are attracted to the same pollinator plants as other bees through the season. They will land on a flower and vibrate their bodies to shake loose pollen which gets caught up in their body hairs. The vibration makes a loud buzzing sound. Being solitary bees, they won’t sting unless they are trapped in clothing or defending a nest. They are easy to spot because of their size, color, slow movement and loud buzzing.
New bumblebee queens emerge each spring and then seek a new nest site. The queens seek out old mouse nests, bird nests, house insulation or other places, above or below ground where dry, fluffy nest material is available. The spot they settled in our rock pile was probably a mouse nest.
The new queen makes a wax “honey pot” in the fluffy insulating material and then fills it with nectar and builds a wax nest next to it. Once eggs are laid, she broods the eggs like a mother hen, warming the eggs and larvae with her body by flexing her flight muscles. This initial generation of workers then takes over nest building and maintenance to build up the colony. Unlike honey bees, the worker bumblebees all take part in brood rearing, nectar gathering or pollen collection. In the fall, the last brood raises new queens and drones that mate and then hibernate until next spring. The rest of the colony dies out. Individual bees can live for about four to six weeks.
Beyond providing a wide selection of nectar plants through the summer, you can encourage bumblebees to nest in your garden by leaving untended areas and bare patches of ground where they can build ground nests. Leaving fall leaves on garden beds provides insulation for hibernating colonies through the winter. Lastly, be observant in the spring and summer of bees flying close to the ground, there is likely a nest nearby.
For more information on bumblebees in backyard gardens, check out this WSU publication at s3.wp.wsu.edu/uploads/sites/2053/2022/08/Washington-Bumble-Bees-in-Home-Yards-and-Gardens-pdf.pdf.