You can learn to love the Orchard Mason Bee

Faith Paterson
Adams County Master Gardener

A few years ago I came upon information on ordering Mason Bee kits. I knew that the European honeybee, which we have largely relied upon for pollination of our fruit and vegetables, has been in decline. I was anxious to try some pollinators that would not succumb to the ills of the honeybee.

Mason Bees (Osmia lignaria) are friendly, docile and fun to observe as they pollinate flowers. They are not aggressive and can be observed closely. The Orchard Mason Bee is metallic blue-black, and about a half inch long. They are native to North America, and specialize in collecting pollen from flowers of fruit trees. The bees nest in holes in wood or in tubes. However, this bee neither connects nor shares nests, nor do they helps protect each otherís young.

Mason Bees work earlier in the spring, because they can tolerate lower temperatures. They are successful pollinators because their bodies are more hairy, so they can carry more pollen. USDA research has shown each Mason bee can do the work of 100 honeybees!


Orchard Mason Bee houses provide a safe place for these pollinators to lay their eggs.

My original purchase was of a canister of filled tubes (with Mason bees inside), and a wooden shelter box in which to place the canister. Instructions were to keep the bee kit in my refrigerator until early March. The wooden shelter box was to be mounted facing the east on an exterior wall, under an overhang, and about 6í off the ground.

The Mason Bee is a solitary bee. Each female finds her own nest tube, and fills it with the next yearís generation. That first year, my bees emerged in late March to early April. The first 1 or 2 Mason Bees in each tube are always males. Their front space protects the females from predation. When the females emerge, they are mated and the male Mason Bees die.

The female Mason Bee immediately visits flowers to collect pollen. She forms a small ball of pollen, kneading it with nectar and her own saliva, places it in the back of a clean new nesting tube, and lays an egg on the ball. She then collects mud to form a partition and repeats the pollen ball egg laying process until she reaches the end of the tube, which she seals with mud. There are between 5 and 8 individual chambers in her tube. She dies shortly thereafter.

During the summer the eggs hatch and larvae begin feeding inside the tube. They make cocoons and become new adults resting in their secure location until fall. They then become dormant and go into hibernation. They require cold temperatures before spring to break dormancy.

It was exciting to see our first batch of newly hatched females building their nests in the canister of new tubes. An interesting phenomenon is that smaller Mason Bees filled in the tiny diamond shaped opening between the tubes with sealed chambers. These smaller bees are one of the 140 species of Osmia in North America. I have never put my filled tubes of bees in the refrigerator over winter, but leave them outside in their wooden box. You can purchase a starter Mason Bee kit online or from several garden catalogs.

National Wildlife Federation magazine for June/July 2015, reports that about 90 species of native bees range in the San Francisco Bay area. Research at San Francisco State University finds that native bees are providing important pollination services for the regionís urban gardeners. "In a test of uncovered tomato plants to be pollinated naturally by wild bees, and control plants which were covered and either self-pollinated or hand pollinated,Ötomato plants pollinated by wild bees significantly outperform the control group, producing more and larger tomatoes."

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