Learn about keeping orchard mason bees. In late winter, hang your mason bee nest against a wall in a sunny location that has morning light. Placing it about eye level is best. That way you can watch them coming and going.

Mason Bee Nesting Tubes

Consider putting the cocoons out near or on the nest in early March. Choose a warm sunny day with little wind. If using the bees for pollinating your fruit trees, wait until the trees are about 25% in bloom. Otherwise look around your garden and neighbourhood to see what is flowering. Imagine your bees visiting 17 blooms a minute in a 100-meter radius from the nest. Is there enough forage? If so, bring out the bees.

Hang around for a half hour or so and watch for the males to emerge. They are a little smaller than the females and have a white tuft of hair on their foreheads. They are cute! Being male, they have no stinger and so are perfectly safe to gently handle as they emerge. They will sit on your hand for a minute before flying off for a long awaited breakfast. If they leave a bit of orange sticky stuff behind don’t be shocked; just a little bee poop as a memento… If you are very lucky and very patient you might find the males huddled together beneath a flower blossom having a snooze.

The females will stay in their cocoons for another few days or weeks, depending on the weather. Hopefully sooner than later. After emerging they will mate almost right away, but it takes a few days for their ovaries to mature. Until then they seem to disappear. Eventually, if you have the right conditions, you’ll see them busying themselves around the nest.

They’re hard to follow, being such fast fliers. You can spot them around fruit tree flowers if you wait long enough. In the afternoon they can be seen with their back ends sticking out of the nest tubes, having a siesta.

For greater success helping your bees, make sure there is exposed clay nearby. Unfortunately, one year my bees used construction-grade sand to make their walls. The next spring the newly emerged bees couldn’t chew their way out. Since then, I haven’t left this to chance. A small tray of water with rocks in it for landing on also increases the bees’ ability to lay eggs. Planting a diversity of flowering material, in terms of colour, height, type of flower, and time of blossoming will give the bees more opportunities for forage.

Adult female bees lay a single egg and deposit a ball of gathered pollen and nectar. Then they wall that chamber closed before laying the next egg and depositing the next food ball. Being parthenocarpic, mason bees lay fertilized eggs—females at the back of the nest tubes, and unfertilized male eggs at the front.

Usually by the end of June, this year’s adult females are dead. You will notice a drop-off in activity around the nest. At this time, it’s worth bringing the nest indoors, and placing it with the entry holes pointing up somewhere out of the way like on top of the refrigerator. This will ensure that the larvae in each chamber will be in contact with their stored food supply. By bringing it indoors, you can prevent the developing larvae from being eaten by birds or parasitized by wasps. Don’t worry about it being too warm, as the larvae need time to spin their cocoons and turn into pupae.

By the end of August the larva have pupated inside their cocoons and are already fully mature. They will stay in this dormant condition until the following spring when the cycle begins anew. By late September, it will be safe to open the nesting tubes to wash the cocoons.

Gently take the tubes apart and float the waterproof cocoons in a bowl of cold water. Delicately rub them back and forth with your fingers until no more mud and mites can be seen clinging to the cocoons. The mites are very small and look like rust, turning the water very red. Cocoons containing live healthy bees tend to float on the surface of the water. Keep the sinkers separate from the good cocoons to see what emerges. This is a good way to get up close and personal with one of the small wasps that parasitize mason bees.

Gently dry the cocoons (mould can be a killer for the bees too), by placing them on dry towels and rolling the cocoons around to remove moisture.

Place the cocoons into a paper bag or cardboard box, such as a Jello container. Place it in the refrigerator or an unheated room until conditions are right in the spring for release.

Article compliments of Brian Campbell, Certified Bee Master.

Update – some answers to questions and comments:

Too late or too early?

Mason bees emerge from their cocoons at exactly the time when early spring flowers are opening. Their brief lives as adults last from March until around the end of June. In late winter/early spring, on sunny days you may see insects flying around. That’s the signal that it’s warm enough to place your mason bee cocoons outdoors. Don’t worry if it rains or gets cold again – these insects are pretty tough. In south coastal BC and the US Pacific Northwest, March is the time when many trees go into bloom and dandelions and Forsythia flowers appear.

You have to play it by ear in regions where winter can drag on. Simply keep an eye out for flowers and early insects.

By July 15th, it’s probably too late to hope for success with mason bees, no matter where you live.

No visible bees?

It’s a very common experience to find hatched cocoons but no signs of bees around the nest. Remember that these are not honeybees. They are solitary, not colony-forming insects. It’s unlikely that you will ever see a male mason bee without a great deal of effort. Only the females frequent the nesting site. They gather enough pollen and nectar to form a food supply for one larva, then they lay one egg and seal the cell with mud. Each of the tubes in your nesting site will hold about six cells. The deepest cells (farthest from the entrance) will harbour larvae that will grow up to be adult female bees. The ones nearest the entrance are males.

Don’t look for “a hive of activity” around your mason bee nesting site. Rather, from mid- to late-June, watch for the tubes’ entrances being capped with mud. That’s the sign that you have a successful nesting site.

By the end of June, the nesting period is over, and the female adults die. If you have mud-capped nesting tubes, bring them indoors at this time, and store the entire nest somewhere out of the way, where it won’t be disturbed. Store it with the entrance holes facing up – this will ensure that the emerging larvae are in contact with their food stores inside each cell. Give the lavae time to mature. By late October or early November, the larvae will have pupated, having spun silken cocoons in which they will lie dormant over the winter months. This is the time to gently remove them from the nest and clean them, removing any parasitic pollen mites and discarding any diseased or dead cocoons. Then the mason bee’s year starts again, with the cocoons being placed back outside near a clean nesting site in March.

Planting for mason bees?

The ideal flower for mason bees is actually that of a fruit tree like cherry, plum, or apple. These flowers are shallow and numerous, and they appear in spring and early summer. If you have flowering fruit trees in your yard, or even in your neighbourhood, it’s not strictly necessary to plant more flowers to feed your mason bees.

However, all pollinators (including your mason bees) benefit from a wide variety of flowers blooming over a long period. If you have room to plant a bed of wildflowers, you will be rewarded by the presence of all kinds of pollinators throughout the growing months, from bumblebees to hummingbirds and butterflies. Planting flowers with wild pollinators in mind is a simple step we can all take to enhance pollinator vitality in our neighbourhoods. Choose a wildflower blend to suit your particular planting needs.