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Solitary Bee Condos

Build a passive solar, backyard habitat for native solitary bees.

 img 0545 Solitary Bee Condos

This project first appeared in MAKE Volume 38, on page 92.

My wife, Colleen, is an urban naturalist. Her summer activities include tending her amazing native garden, raising monarch butterflies, and lately, building condos for solitary bees — bees that nest independent of a colony. Colleen first became interested in these bees when she saw them nesting in small pits in the bricks on the front of our house in Toronto. It turns out that of the 4,000 species of bees native to North America, over 1,000 are tunnel-nesting bees — they lay their eggs, provision them, and seal the entrance inside natural tunnels such as hollow plant stems and insect bore holes. Not every native bee is a solitary bee, and not every solitary bee is a tunnel nester.

Native bees are important pollinators and make a significant contribution to agriculture. Non-native species, such as the European honeybee, have been employed commercially to pollinate crops but have, in recent years, been subject to devastating diseases. The Delaware Department of Agriculture estimated that “native bees were responsible for pollinating 3 billion dollars in crops in the U.S. in the year 2000. … Encouraging native pollinators is a pollinator insurance policy.” The type of native bees attracted to your bee condo depends largely on where you live. In Toronto, our condos attract mainly cellophane, masked, mason, and leaf-cutter bees.

3 bees Solitary Bee Condos

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Steps

Step #1: Design your condo.

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Solitary Bee Condos

The most popular styles of solitary bee homes are nesting blocks and stem bundles. A nesting block is a wooden block with a series of blind holes drilled parallel to the grain with a sharp drill bit (bees like smooth holes and won’t lay eggs in an open-ended tunnel). A stem bundle is just what it sounds like: a series of tubes sealed on one end, either lashed together or held in a container. I’ve chosen this type for my project.

Step #2: Build your condo.

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The 2 major components of my condo are the roof assembly and the stem bundle container. The roof assembly was made from some walnut hardwood scraps and pine molding. Here’s what I used:

  • Backboard — 6"×6"×¼"
  • Roof — 6"×4"×¼" (2)
  • Roof supports —½" quarter-round molding: 5½" long (2), 4" long (1)
  • Roof ridge— wood dowel, 3/8" diameter, 4" long

Step #3:

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  • The roof keeps the stem bundle dry, discouraging fungal growth that can kill the bees. Adjust the roof dimensions, if necessary, to overhang the end of your stem bundle. Seal the roof assembly with 3 coats of tung oil to weatherproof it.
  • The bundle container is a discarded nut can (a plastic bulk CD container also works well) spray-painted black to warm up more quickly in the morning and retain heat during the day(this is the passive solar aspect). Bees are cold-blooded, and the morning sun gets them up to operating temperature.

Step #4:

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  • I’m using untreated bamboo garden stakes, but paper drinking straws, reeds, or bundles of most any small-diameter tube can be used. For more details, see the Resources at the end of this article.
  • My condo contains about 130 bamboo stemsof varying lengths, from 3" to 3½"; larger condos may require 5½" to 8" stems. I used most of a package of 15"–36" garden stakes. It’s important to cut the bamboo close to the nodes (the swollen part that the leaf grows from), as there is a dividing wall at this point that will form the closed back end of each stem.

Step #5:

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Close one end of any open-ended stems by dipping them in white glue and letting them dry. Open any blocked stems by pushing a bamboo BBQ skewer into them up to the node.

Step #6:

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The bamboo stems are friction-fit in the container (pack them tight and check them occasionally for shrinkage), which unscrews from the roof assembly for periodic cleaning.

Step #7: Mounting and maintenance.

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Solitary Bee Condos
  • Bee houses should be located on the east side of the house for morning sun, and sheltered from the rain. Although according to Dr. Vicki Wojcikfrom the Pollinator Partnership, “In hot climates a north-facing location might be better, to avoid cooking the bees.” They can also be mounted on a post or pole.
  • I suggest you hang them at a comfortable height for viewing and keep them clear of vegetation. Different-diameter tunnels will attract different species, and it’s fun to watch them come and go, or to try to identify the various types of bees.
  • After a couple seasons, bee houses should be disinfected to prevent the spread of parasites and fungal disease. My bee condo disassembles easily for cleaning and maintenance.

Step #8: Resources

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Solitary Bee Condos

Ken Vickerson

Ken Vickerson is an associate professor in the faculty of Design, and chair of the Material Arts and Design program at OCAD University in Toronto.


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