Mason bees look for tiny holes in the wild to lay their brood. Bee-friendly places might be holes bored into trees by other insects or the stems of dried reeds and other plants. Ideally, the hole should be around 8mm (around the width of a pencil) and 3-4 inches deep.
The female bee will collect pollen and place it in the hole, then lay her egg, then seal up the development chamber with mud — hence the name mason bee. She repeats this until 5-6 eggs have been laid in that hole. A female mason bee will lay around 15-20 eggs in her lifetime.
Beekeepers can help support the mason bee population by providing artificial holes, into which the insect can lay her eggs.
The mason bee house
The basic design of a mason bee house consists of some sort of container that provides shelter, similar to a birdhouse, with an opening filled with access holes to hold brood.
There are quite a few options when it comes to choosing a mason bee house. There are tons available to order online or there are many DIY options.
The type of chambers you choose depends on how invested you want to be in your mason bee population. You can let nature take its course and have a more hands off approach, or for a more successful population, you can keep a house where you clean the chambers at the end of each season and remove the cocoons for controlled over wintering. See my post How to Harvest Mason Bee Cocoons for how to accomplish this in eight simple steps. The type of house you choose will determine how easy it is for you to access the cocoons and clean the holes. The brood chambers are typically offered in three ways.
Wood with drilled holes
Sometimes the house is a solid piece of wood with holes drilled into it. This is if you want nature to run its course. This type of house will yield the least results as far as an increase in population. It will also only be able to house the bees for 1-2 seasons.
Another option is a stack of paper, cardboard or reed tubes. This is the most common, and perhaps the most cost-effective way to raise Mason bees. Some people line more permanent tubes with paper for easy removal and save the more structural tubes from year to year.
There are also trays available These are perhaps the most expensive to purchase, but the easiest to take care of. If you have a good router bit, these would be simple to make yourself.
The trays are nice in that you just need to un-stack them for access to the brood chambers.
The mason bee house should be placed 6-7 feet off the ground facing the southern sun.
Though most mason bee houses are equipped with a roof-like shelter, the bees will appreciate being placed under the protective eaves of a house or under rain-blocking tree branches.
The house should also be placed less than 300 feet from a good source of nectar. Bees prefer native species of plants, and these provide the most food. You should also consider if these plants have staggered bloom times. You don’t want the bee’s food to present itself all at once and then they will have nothing to eat for the rest of the growing season.
If you live in a dry area, the bees will appreciate a source of clay based mud that is moistened often. From this, they will collect their “masonry supplies” to create the divisions in the development chambers. Anything that you can do to make your bees more successful will ensure a healthy population.