Most of us who want to attract native bees to our yards and gardens do so by providing housing in the form of tubes, straws, hollow reeds, or drilled wood. While there is nothing wrong with this, the irony is that fully 70%—or nearly three-quarters—of all bee species live underground. Above ground cavities are completely useless to most bees.
So, if we really want to attract a variety of bees, we need to prepare space for the ground-dwellers. This is not an easy task, which is why it is frequently overlooked.
Many people don’t have land available for bee habitat. Some folks live in apartments, condos, or subdivisions where it is easy to have a few drinking straws on the porch but impossible to have a patch of bare earth. Others live in areas where bare earth is considered an eyesore. Still others live where the soil is mostly covered in asphalt and concrete. Nevertheless, there are things we can do.
What the bees need
Ground-dwelling bees like sandy soil, such as sandy loam, that is damp but not wet. It should be bare—free of plants and their annoying roots. It should be gently sloped, about 30 degrees is nice, and should face south or southeast in a sunny location. In addition, it should not be covered with mulch of any type. But here is the kicker—something that’s easy to forget: it must remain undisturbed nearly all year.
Why undisturbed? Because unlike honey bees, most native bees hibernate underground for about ten months of the year. They spend this time as a pupa or an adult, depending on the individual species. If we disturb their nests by tilling, disking, or shoveling the soil, we kill the bees.
How to do it
Researchers have found that even small bare patches can be useful for bees. While some native bees nest in large aggregations containing thousands of nesting holes, others build off by themselves wherever they find a good spot.
You can build “scrapes,” which are simply patches of earth with the plant life scraped free. You can build forms out of wood or brick, and fill them with sandy loam sloped toward the sun. Or you can truck in soil and just mound it in a sunny location.
Even a flower pot can be used. So if you live in condo with a balcony, for example, you could have several pots with flowers and one with bare soil that you water occasionally. Dampness is necessary for the bee tunnels to maintain their shape; if the soil gets too dry, the tunnels may collapse.
The sandy loam should be about 50 to 70% sand. Since you are not growing plants in it, the percentages of clay, silt, and organic matter are not too important. To make loam for bees, in most cases you can just take your native soil and mix it with an equal amount of sand.
When will they come?
In a study in Oxfordshire UK, where they dug four 3 x 5 m nesting plots, solitary bees nested in the first year. During the next three years, 80 different species of solitary bees and wasps colonized the plots [1]. Other similar experiments in Europe and Oregon have produced nests during the first one to three years.
Give it a try
If you decide to build an underground bee bed, take some photos and let us know what you did. This is new territory for most of us, so any hints, suggestions, or bee stories would be especially welcome.
Rusty
HoneyBeeSuite
[1] Gregory S. & Wright I. (2005) “Creation of patches of bare ground to enhance the habitat of ground-nesting bees and wasps at Shotover Hill, Oxfordshire, England.” Conservation Evidence, 2, 139-141.
This large managed alkali bee bed is in Touchet, WA. The pipes you see are for underground irrigation that keeps the soil slightly moist. The white on the soil surface is salt, the requirement that gives alkali bees their name. The bees that live in the bed pollinate the alfalfa fields that you see in the background. © Rusty Burlew.
This tiny sandbox for bees is at Oregon State University. The soil was taken from the university golf course where a large natural bee bed was discovered in a bunker. © Rusty Burlew.
Remember: sunny, south-facing, gently sloping, sandy loam, no vegetation, slightly damp, no mulch, leave undisturbed.
Cats! I think the neighborhood cats would enjoy a weed free sandy box. Maybe a wire topping? Sounds like a project, thanks.
Sheila,
You are right, of course. I thought about that briefly and then forgot. Yes, a cat guard sounds good.
Thanks, this is good information. My back yard is mostly sandy loam. I’ll have to make some bee homes 🙂
John,
Perfect soil for bees. I’m jealous!
I’m so excited to try this in the spring! I volunteer at a food bank farm on a decommissioned golf course and we’re making a concerted effort to support native pollinators there. I’m their pollinator expert, keeping honeybees there as well as teaching mason bee classes and basically talking about bees whenever possible with whoever will listen. I really look forward to being able to bring in the angle of how prevalent ground-nesting is among solitary bees, as well as showing people how to support them. Love this blog, Rusty! You’re such an invaluable resource.
I think I can see how to make such a spot — just tear the plants out, then keep it damp and hand-weed it like a garden. But how do such spots occur in nature? It seems to me that any sunny spot that stays slightly damp will not long remain free of vegetation. Perhaps in a forest, where the trees shade out most of the grass? But then the spot wouldn’t qualify as “sunny.” Or does it not have to be all that sunny?
Sean,
Bees evolved in deserts and dry places where bare patches are normal. There is a patch of mining bees near me that I watch every year, right in the middle of a gravel road. They find ’em. They also like playgrounds and baseball diamonds.
Thank you for the informative article. Over the years, I have moved all vegetation away from the foundation walls of our old house to ensure the lathe and stucco walls air freely on the wet, west coast. An unexpected effect and benefit is to have this broad band of sandy soil around the house become home to many underground bees.
Husband and I also appreciate the clear pathway access for never-ending home repairs and gently place stools and ladders to avoid the bee nest exit holes when they are most active in the spring.
I am new to your website and have referred all my students and colleagues to it as a great source for use in classroom and community education programs.
Regards, Ann.
Ann,
That sounds lovely and your message is such a wonderful change from the “How do I kill them?” question I usually get.
I’m glad you find my site useful. Suggestions for further topics are always welcome.