February 12, 2020 4 min read

Mason Bees are solitary nesting bees that are native to our area. Did you know that they are the main pollinators of fruit trees in the Portland area?

You can host these gentle bees in your own backyard. Keeping Mason Bees is an inexpensive and fun way to get started with beekeeping.

Being a Mason Beekeeper does come with some responsibilities. Since you are hosting them in the same spot every year, you will need to protect them from harm.

Setting up a Mason Bee House

Fill the main compartment of the house with as many cardboard tubes or hollow reeds as will fit. Leave the top, or “attic,” clear of tubes. That will be a great place to put cocoons before they hatch.

It’s important that the house has an overhanging roof to keep them from getting wet in the rain. Tubes should be around .3 inches (8mm) in diameter and at least six inches deep.

Hang the house securely against a fence or building, well off the ground, where it will be easy for you to see the bees coming and going. You will also want it to be easy to access since you will collect and replace the tubes later in the year.

East-facing is the best direction, but south-facing will work if they have some protection from the hottest afternoon sun. The bees will want to warm up first thing in the morning, so that morning sunshine will help get them going.

If you are starting with purchased cocoons, put those in the attic of the bee house as soon as temperatures start to warm up in spring. Mason bees will start to emerge once the air temperature reaches 55 degrees for a few days in a row. (Watch for fruit trees blooming.) You may want to stack rocks or pinecones in front of the cocoons in the attic to keep the bees safe from predators.


These bees will only fly a maximum of about 300 ft from the nest. Therefore, it’s important to have many flowers blooming during the time of year that they fly (roughly March to June.)

Make sure that there is some moist, open clay soil available to the bees as close to their house as possible. They are called “Mason Bees,” because they use mud to build walls between individual egg chambers.

Life Cycle

There is one generation of Mason Bees raised every year. If you are starting with cocoons, those will hatch and the bees will find the tubes you provided right away. The males and females will mate right away, after which the females will start collecting pollen and laying eggs in the tubes if you have the right resources in your garden.

If there is enough mud, nectar, and pollen available the bees will stay and build their nests in your tubes. Females will start by collecting pollen, making a pollen loaf, laying an egg on it, and then building a wall of mud. They will repeat this process until the entire tube is filled so that each baby bee will have its own chamber. Female bees will be deeper in the hole, males will be laid closer to the outside. (Make sure your tubes are at least six inches deep so you are sure to get female bees.)

After about a week, the egg will hatch and the larva will start to eat the pollen. After around 10 days the larva will have eaten enough food. They will spin a cocoon and start changing into full-grown bees. This transformation takes until the end of summer, but the bees will stay in their cocoons until the next spring.

Beekeeper Tasks

Keep an eye on your bees all season, making sure no birds or other predators are intruding.

If predators become an issue, you might want to try installing one quarter inch hardware cloth over the face of the house. This will allow bees to go in and out while also protecting them. (Make sure you will still be able to get the tubes out at the end of the season too!)

In October, start collecting your tubes of bees for safe storage over winter. Create a small work station where you can open the tubes and look through which cocoons are viable.

Throw away any dead larva that did not spin a cocoon, they will look like half-moon shaped grubs. Throw out any cocoons that have holes in them (this is a sign of wasp intrusion). Separate out the cocoons that look healthy. They will be light grey and oblong.

Once you have all your healthy cocoons in one place, shine a flashlight into each one to make sure there is a bee inside, not a beetle. There’s a type of beetle that will take the place of bees and you do not want to let them into storage.

Mason Bee cocoons are water-tight, so you can swish them in water (50 degrees or less so they don’t wake up!) to make sure they are clean going into storage. Air dry on a paper towel for 10 minutes.

Keep them in a container in your refrigerator over winter. Make sure it is not air-tight, they need to breathe, and add a bit of moisture every couple of weeks so they do not dry out. You can use a damp paper towel or piece of sponge to hold the moisture.

Come spring, put out fresh cardboard tubes in your Mason Bee house and place your cocoons in the attic. Your bees are ready for another year!

We’ve got Mason Bee nesting materials, houses, books about habitat, and cocoons to get you started and keep you supplied year after year.