Solitary bees are pretty damn awesome: They’re docile, easy to raise, and are amazing pollinators of spring flowering fruit and nut trees. These bees don’t use hives the way honey bees do, instead preferring to place their eggs in narrow holes, plugged up with mud.
Their gentle nature and solitary habitat preferences make solitary bees a great species to “keep” in your yard. That is, if you do it right. If you don’t do it right, you might be harming them more than you’re helping them.
Former evolutionary biology professor Colin Purrington took to Twitter earlier this month to tell us all the ways our good intentions have gone awry.
I'm seriously sick of seeing bad mason bee houses for sale. It's like selling bird houses with built-in observation platforms for cats. They'd be super cute and everyone would post on Pinterest but would cause birds to be eaten.
— Colin Purrington (@colinpurrington) May 3, 2019
If you’re leaning toward a store-bought variety, don’t simply grab the first cute structure labelled “solitary bees” that you see. It’s important to educate yourself about the insects first to understand how to most effectively help them — and not accidentally harm them instead.
Clean their house every autumn
The biggest problem Purrington points out with some store-bought solitary bee houses is that the blocks and reeds are glued to the back of the house. That means you can’t add new nesting material each spring, greatly increasing the risk of parasites and fungus.
You’ll find some great info here on the year-round care of solitary bees, including storing the nesting tubes and blocks and harvesting the cocoons.
Location, location, location
Solitary bee houses should be placed against a flat surface in an area protected from high winds, approximately 2m off the ground and south-facing if possible. Do not hang mason houses by a string from a tree limb; allowing the eggs to be knocked around in every passing breeze isn’t helpful.
They’ll also need to be close enough to pollen-producing plants (they won’t travel farther than 90m), as well as a good supply of claylike mud to cover up their nesting holes.
Give them a little overhang
The roof of a good solitary bee house will have a bit of an overhang to protect the holes from rain and lower the risk of the larvae and pupae rotting inside the nest.
If you’re now questioning the quality of your solitary bee house, you can always ask Purrington directly for his opinion (hey, he offered):
But here's the good news: there are a lot of great mason bee houses for sale online. I don't currently have a list of these handy (sorry), but if you find a house that you'd like me to inspect, send me a pic or link via email: https://t.co/m665jhpFzD.
— Colin Purrington (@colinpurrington) May 4, 2019