These bees are solitary and not aggressive—they do not build colonial hives like honeybees, and they will sting only when highly provoked (captured in the bare hand, for example). “You can be right next to these bees as they fly around and they basically ignore you,” says Trent Toler, an entomologist who worked for several years at the USDA Bee Lab at Utah State University in Logan.
If you don’t have the inclination to tend a hive and reap the benefit of honey (as well as suffer the stress of death, disease and loss, should your colony collapse), you can still help out the pollination effort with a minimum of care and cost. Trent says you can attract these gentle workers to your garden.
First, make sure you have a good variety of flower species (in addition to your crop species) for the bees to feed upon; and, most important, provide nesting sites for them. “Many of these native bees are twig-nesting,” he says, “and the main limiting factor on the population is how many nest sites exist at a given location.”
A few years ago, Trent noticed that some native leafcutter bees were nesting in screw holes on his porch from where an awning had been removed . “The holes had been filled in and the ends neatly papered over with bits of leaf.”
Wanting to encourage these native pollinators in his garden, Trent made a “bee block” nest site for them out of a block of scrap wood.
“I took a 4x4-inch piece of untreated lumber about 18 inches long, and drilled a bunch of holes into the front of it with a 13/64ths-inch drill bit,” he says. “It was as simple as that.”
The bees moved in and filled the holes with nest cells—each drill hole might house five or six cells, with each cell containing a single bee egg and a ball of pollen ready to feed the young bee larva when it hatches. Trent suggests helping the bees stay healthy by providing new blocks every year.
Native bees are so popular with gardeners now that you can buy them online. Mason or blue orchard bees (Osmia lignaria) are available for purchase at several different sites. April is a good time to order the bees, as they typically emerge in May, just in time to get to work in your garden. $48 will get you 40 bees; that will make as many bees as you give them housing for.
“Mason bee houses” are also on sale at many gardening sites, and even from Sears and Kmart. These are fancier versions of the bee block that Trent made for himself. Some come with replaceable paper straws for the cells that will allow you to get multiple disease-free years out of a single block.
“Encouraging native bees is mostly a matter of paying attention to what’s going on in your garden already,” he says.
Besides the leafcutter bees, Trent also found a species of ground-nesting native bee in a patch of bare soil in his front yard. “The ground-nesters are less common, but you can find them in flat, packed, clay soil — you’ll see many little round burrow-entrances in it. During the growing season, bees will be flying in and out of those burrow holes all day, provisioning them.”
If you find ground-nesting bees in your garden, leave them alone. “The bare soil might be a little ugly,” he says, “but you can just put a little border around it and tend your plants somewhere else, knowing that your garden is being well-pollinated!”
Create a simple house for native leafcutter or mason bees
- block of plain pine, fir, or hardwood (avoid pressure treated, cedar, or redwood), 4x4 in., any workable length
- drill with sharp bits of varying sizes: 13/64, 7/32, 1/4, 5/16
- pen or woodburning tool
- beeswax, foil tape or water-based polyurethane sealant
Trent recommends first-timers use a few different sizes of drill bit; different bees prefer different-sized holes, and you likely don’t know what species of bee you have in your area. Use a sharp bit so the hole insides are as smooth as possible.
Marking the front of the block with irregular patterns will help the bees navigate and remember whose hole is whose.
To keep parasites out, seal the back and ends of the block with the beeswax, tape or sealant.
Where to hang: Choose a sheltered place with some sun but not too much. An east-facing porch is perfect.
Happy native beekeeping!
Instructions for building a mason bee house:
USU-USDA Bee Lab: http://www.loganbeelab.usu.edu.