Bees bring a new dimension to your garden: they’re interesting to watch, are easily bred and are the main pollinators of our fruit trees.
In particular, the native mason bee (Osmia lignaria) can be enticed to stay in your garden by adding bee boxes, which are also a boon for these beneficial buzzers since natural nesting sites are often scarce. Because these specific bees only use pre-existing cavities, the basic nesting requirement is a hole-like structure in wood or another material.
Building a bee box is as simple as drilling holes into a piece of wood or making your own nesting straws. You can also buy nests made out of plastic that fit together and can be cleaned. Ones that can be opened and cleaned (such as the nesting straws or trays) are better for producing healthy mason bees each year.
The box should be set out in early spring. As the eggs hatch, the larvae will then create cocoons in which they will mature over the summer; they will remain in these cocoons over winter, emerging as adults in spring.
In late fall, to keep the cocoons safe from pests and preserve them for next spring, it’s essential to gently transfer them from the nesting straws into a dry, cool place—such as a can with a lid—and store in a shed or unheated garage (a basement would be too warm). In early spring, carefully place the cocoons into new nesting tunnels and back into the bee box to begin the process anew.
If there are local mason bees, they will find the nest. Otherwise, starter bees (males and females) may be purchased from your local bird store or garden shop.