For mason bees, the wait for their first meal is a long one—nine months or more—while they wait to emerge from their larval stage, sun themselves a bit and fly off for an awaited meal. These solitary bees hang out in their cocoons waiting for early spring’s cool temperatures to break them out of lethargy.
Because honeybees and other pollinators haven’t made an appearance yet, there’s more sweetness for the native mason bees.
“Mason bees fill a spot in the season when other pollinators like honeybees are not out,” says Brooke Edmunds, a horticulturist with Oregon State University Extension Service. “They’re really important for fruit trees.”
After emerging in March, the small, bluish bees start foraging for food for the next generation and combing for suitable nesting sites.
“They’re solitary, nonaggressive bees, so they’re very different from honeybees,” Brooke says. “They don’t form hives.”
Instead, mason bees—most commonly the native blue orchard mason bee (Osmia lignaria)—look for cracks and crevices that fit their need for small spaces where they crawl in and lay eggs. They might find spots in wood bored by other insects or siding on buildings. Gardeners can also buy tubes of cocoons containing larvae that will hatch into adults. The tubes are inserted into nesting blocks that are hung in the garden.
Be aware of what’s blooming, starting with willow and big leaf maple, followed by other early bloomers such as fruit trees. Because the bees need a continuous source of food, make sure there will be something blooming throughout their three-month lifespan.
You can get elaborate and remove the cocoons each fall, clean them, store them during winter and reinsert them in the tubes in spring. Or choose the easy way: Hang the tubes and wait for the bees to find them and lay their eggs. You can also buy new cocoons each year.
For protection against mites, keep loose cocoons in small cardboard tubes that look like straws with holes just big enough for the bees to fit through. Gently place the tubes in the holes of the nesting house. Hang the nesting house in the yard, preferably in morning sun under an eave so it’s sheltered from rain and wind.
Mason bees’ preferred food comes from early blooming fruit trees such as apples, pears, plums and cherries. Plant one or two to attract them to your garden to pollinate other plants.
Other plants also attract them. Look to crabapples, flowering currant, elderberry, huckleberry, forsythia, Pieris and Oregon grape. Mason bees will head straight for dandelion, which are abundant in spring.
Because mason bees travel only short distances—about 200 to 300 feet—their favorite plants need to be planted near nesting spots or they will leave.
You also need to provide small patches of clay mud. If you’ve covered your soil with mulch, push away a little to create a mud pool for the bees. If the soil dries out, give it a misting. Alternately, put a tray out and fill it with moist clay soil.
The female mason bees use the clay soil to wall up their eggs, which are deposited in the tubes or crevices with nectar and pollen they’ve rolled into little balls. They will continue to alternate wall, food, egg and wall until they come to the end of the tube or crevice, then close it up for the next nine months. The eggs develop into small larva that spin cocoons where the adults form. Come spring, the adults break through the cocoon, chew through the clay and fly out to start the process again.
In their short life, these single-minded bees do an important job for gardeners. Most significantly, they efficiently pollinate prized fruit trees, giving a markedly increased yield. But consider a more altruistic reason, Brooke says. Mason bees, like other beneficial insects, help diversify the garden, leading to a healthier backyard ecosystem, healthier humans and a healthier planet.