What are Mason Bees?

There are many different kinds of pollinators. You already know about honey bees, which gather nectar and pollen from flowers, then deposit honey into honeycombs in their hive. The mason bee (Osmia lignaria in the Pacific Northwest) doesn’t have a hive. It doesn’t create honey. But it does one thing even better than the honey bee. It pollinates the plants that produce a lot of the food we eat. If you eat apples, pears, cherries, nuts and berries, chances are mason bees helped produce them.

Mason bees nest in holes in wood or straw, or in “bee houses” people put out for them.

After hatching, the larva eats a “power bar” left by the mother that is made up of nectar and pollen. The mother bee might make as many as 30 trips back and forth from the hole to the flowers to provide for each egg she lays.

The mason bee might look like a house fly, unless you observe carefully. It has a similar blue-black color like a house fly, but its wings and body are different, and so is its behavior.

Hosting mason bees in Portland

Hosting mason bees is a simple, rewarding, and fantastic way to support local pollinators and boost the health of your garden - and the broader urban orchard we like to talk about. These gentle, solitary bees are easy to care for, require minimal maintenance, and can increase the yield of fruits, vegetables, and flowers in your neighborhood. They are also great fun to watch in the spring when the trees are often far less interesting.

You can get as adventurous as you like with the construction of their houses, but even a simple structure that gets them up off the ground (away from chemical sprays and predators) is super helpful! Stay tuned for a spring workshop to learn to build your own mason bee houses, or check out Crown Bees if you prefer to buy your bee accomodations.

Building a Mason Bee House

You’ll need a structure with tubes or blocks of wood with holes, ideally 6-8 mm in diameter, where the bees can lay their eggs. You can buy pre-made tubes or create your own using paper straws or bamboo reeds. Make sure the house is weatherproof, with a roof to keep rain out, and place it on a stable surface.

Mount the house in a sunny spot, ideally facing east or southeast, and at least 3-5 feet off the ground. It’s best to secure it to a wall, fence, or tree trunk. Mason bees are most active when it’s sunny, and they need the warmth to thrive.

Timeline for Hosting Mason Bees

1. Early Spring (March - April): Put out the mason bee house (follow Portland Fruit Tree Project or sign up for our newsletter to find out when we will build bee houses and distribute cocoons next season!). In Portland, this is when the temperatures begin to reach around 55°F consistently: the warmth signals the bees to emerge from their cocoons, which you can pre place within the structure so they can get bee-sy when they’re ready to start nesting.

2. Spring (April - May): As bees start to emerge, they’ll “bee” gathering pollen and nectar to feed their young. This is also the time they will lay their eggs in the house, which will develop into larvae and eventually spin cocoons by the end of spring. Ensure you have plenty of blooming flowers nearby to support them, also, creating some mud nearby for them to use in their cocoon building is extra supportive!

3. Late Spring - Early Summer (June): By now, most of the bees will have completed their nesting. You may notice that the house is sealed with mud—a sure sign the larvae are developing inside. You can leave the house up through summer, allowing the young bees to develop and remain in their cocoons. Provide an extra barrier by putting the house in a mesh bag or covering the openings with old panty hose!

4. Fall (October - November): Harvest the cocoons. Remove the tubes or open up the drilled blocks to carefully extract the cocoons. Gently clean them to remove mites or other pests, and store them in a ventilated container in a cool place, like a refrigerator, until the following spring. This step can be a little intimidating, s we hope you’ll join us in learning more!

Hosting mason bees is an enjoyable and rewarding experience that directly benefits your garden, and as you build your experience year after year, you can share cocoons to increase healthy bee populations in our community!

WANT TO ATTEND our group bee harvest event?

1. JOIN our group harvest and learn event 10.19.24 11am at Parkrose Orchard by registering here!

2. Make sure you are on our mailing list (pop up to plug in your email is on our main page) so that you are alerted about 2025 Bee House making dates!

3. We recommend Portland Nursery and Crown Bees for all of your Mason Bee supplies! Check out all of the great info on their website to learn even more. https://www.portlandnursery.com/garden-projects/masonbees
   
   
   

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