Providing Homes for Mason Bees

Mason bees are solitary but gregarious. Each female builds her own nest, but they like to nest in the same area with others. Here are two returning to nests they have found in the cracks between tongue and groove boards that have shrunk over the years. These bees become active in the spring, when fruit trees bloom, and they finish their life cycle in early summer. This makes them good fruit pollinators, but not for later veggies. You can see the bright yellow pollen on the belly of the upper bee.

In our backyard there is a dead tree. Enough has been removed to make it safe from falling on a building or vehicle, but the remainder was left. It serves as a home and feed source for woodpeckers (and also helps to keep them from going after good wood). If you look carefully you can see three nest holes, and other places where the woodpeckers have fed.

We are also going to provide some housing for our local mason bees. (Of course, there's a chance they could become woodpecker food, but that's the way nature is.) They cannot drill holes as do carpenter bees, so they must find existing holes, such as hollow reeds, spaces under shingles, cracks in buildings, etc. We could drill holes in blocks of wood for them, or we could bundle straws or stems of some wood with soft piths, such as elderberries. Some folks make holes in adobe blocks, or drill into morter joints with a masonry bit, in places where it won't hurt a building of value. Using this dead tree is an easier choice for the moment.

The ideal drill size for mason bees has been found to be 5/16 inch. Other sizes can be tried and may interest other species of bees or potter wasps, which are also beneficial. A standard drill bit is not adequate, because the hole needs to be at least 6 inches deep. I could only find a 12 inch drill, though I would have preferred an intermediate length.

We should have made these when frut first began to bloom in February. It is late now, but mason bees are still active here in South Carolina, so we are hopeful they will be used. Early April is a good time for the northern part of the USA.

Drill slightly upward so that water cannot run into the nest and drown the baby bees. The holes must be drilled at least six inches deep to achieve the proper ratio of males to females in the next generation. After the hole is completely drilled, run the bit back thru to clean out all shavings.

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Clusters or groups of holes are made within an inch or two of each other, so the bees can have neighbors nearby when they are working.

We will continue to report on this page, if the holes become occupied.