I have a small back-yard vegetable garden. I’ve tried to keep that garden attractive to bees. Partly, that’s for pollination. Partly, that’s a good way to avoid using the worst and most persistent pesticides.
This post explains why I’m not going to be putting out a “bee hotel” in my garden this year.
Not only do these bees do nothing for my garden, I’m not sure I’m doing them any favors by providing such a large number of nesting sites.
Two years ago, I bought a little bee hotel at Home Depot. In theory, this array of narrow, closed-ended tubes provides nesting sites for local native and solitary bees, e.g., mason bees, orchard bees. (But not social bees, like honey bees or bumble bees.)
And, sure enough, about half the nesting tubes in that Home Depot bee hotel ended up filled, the first year I hung that up. As shown at the left.
(I now know that this is a terrible bee hotel design and I would never buy it again. The tubes are too short (4″), which apparently leads to an excess of male over female bees. And they’re glued in place, and so cannot be replaced annually with clean nesting tubes, as everyone advises.)
Regardless, the picture above bodes good luck to this location, w/r/t/ mason bees. A lot of people hang one of these up and get nothing, at least for a year or two. But I followed all the directions, and hung that securely, a few feet off the ground, in a sheltered location that gets morning sun, with plenty of flowering plants nearby, and a nearby source of mud for the bees to use. (That last one courtesy of some slightly leaky rainwater barrels.)
Following standard advice, I took that bee hotel down for the winter and left it in an unheated building.
Then I killed my overwintering mason bees.
I killed them with kindness.
My unheated outbuilding must have been just a touch warmer than the surrounding area. In any case, by all the signs — average daytime temperature, extent of blooming flowers — my bees emerged early, as explained in Post G24-004. Just as the crocuses were starting to bloom.
If that didn’t kill them outright — from the low temperatures and lack of blooming plants for food — then it almost surely prevented them from reproducing. Again, as explained in Post G24-004.
The moral of that story is, resist the urge to shelter your overwintering bees. Let them freeze along with everything else.
One year ago, for my second attempt, I made my own bee hotels. I used 6″ long bamboo tubes, cut from the green bamboo growing in my back yard (Post G23-015). (Cutting them green gave them a smooth, splinter-free finish that did not require (e.g.) sanding. Apparently, you don’t want to leave rough edges on these tubes, or they’ll cut up the bees’ wings.)
( You will see mentions of a lot of plants whose stems can, in theory, be used for bee nesting tubes. I tried growing a few (e.g., poke weed), but I learned the hard way that, as with bamboo, your only realistic option is to harvest the material green, and immediately cut it to length. If you wait until spring to go looking for some, all those hollow stems will be weathered and brittle, and you won’t be able to get nice smoothly-cut 6″ pieces from them.)
I closed off one end of each tube with some mud.
Locally-sourced.
Then bundled a handful of such tubes together with wire ties (and later, jute twine).
And hung up my nice new bee hotels, under the eaves of my back porch.
These were an even bigger hit with local mason bees. As you can see at the left, almost all the nesting tubes were filled. Only a handful of empty tubes are left, and by eye, these seem to be too large for my local mason bees to want to use them. (Bees are quite picky about what size of nesting tube they will use.)
Similarly, I made and hung one more bee hotel with much smaller-diameter tubes. This would have been attractive to smaller “leaf cutter” bees that might be present in my area, mid-summer. But I got no takers for those smaller tubes — that 4th bee hotel remained completely empty.
This year, I put those filled bee hotels into a “bee emergence box”.
This is just a dark box with some holes cut out of the sides, level with the bottom of the box, as shown, left. (Level because the newly-emerged bees don’t fly out of the box, they crawl to the opening and hang out there for a while before dispersing. That, according to the University of Utah extension service (Google link to .pdf).
Exactly why I need to supply a bee emergence box seems subject to some uncertainty. Some experts say its to “avoid predators”. (I assume the newly-emerged bees are fairly helpless.) Some say the box must be placed directly adjacent to new bee hotels (with fresh nesting tubes) and that neither should be moved, even a matter of inches, once emergence has begun. Some say that the box allows female bees to find their way back to this location, as they can smell the old cocoons, but the box keeps them from re-using the old nesting tubes.
In short, all experts agree this step is good. But exactly why it’s good, and what purpose this serves, seems unclear. Somewhat folklore-ish. (And clearly related to the naughty bits bee reproduction in some fashion, possibly explaining reticence on this subject. But everybody agrees that such a box is a good idea.)
In any case, below are my home-made bamboo bee hotels, carefully and gently placed in my simple emergence box, before I closed and sealed the lid.
FWIW, one bamboo tube had a little tiny perfectly round hole drilled in it. I’m pretty sure that was an instance of parasitic wasp predation, so I removed that one nesting tube as I placed these in the emergence box.
Apparently, the point of all the darkness is so that the only light entering the box is from the holes that I want the bees to use, to exit the box. And, because this sits in a sheltered location (under the eaves of my porch), I’ve done the easiest thing and made the release box out of cardboard. (Interestingly, I found scant details on release boxes, as if such details hardly mattered.)
Why I’m not putting out multiple bee hotels again this year.
First, these bees do my garden no good whatsoever. These orchard or mason bees will have come and gone long before anything in my garden is blooming. If I had an orchard, with lots of early-spring fruit blossoms, encouraging a local population of orchard bees would be a good idea. But as it stands, these bees will have emerged, mated, and died a month before anything in my garden is blooming.
These are not the bees you’re looking for. … Move along.
Second, it’s not clear that I’m doing them any good, either. Mainly, it’s not clear that nesting sites are the limiting factor for my local mason bee population. There really isn’t all that much around here blooming in late March. And so, I wonder if in effect, I may be raising bees, simply to have them die off soon after they emerge, because there’s no link between the number of bee hotel tubes that I provide, and the size of the local early-spring flowering plant supply.
I found no guidance whatsoever on “right-sizing” a mason bee hotel, to match the resources available in the surrounding area.
Conclusion
There’s not a lot to providing nesting sites for solitary bees. You just have to obey a few simple rules.
The nesting tubes should be about 6″ long, for the most common mason bees. The tubes need to be of about the right diameter for the bees you are trying to attract. In my case, maybe 1/4th to 3/8ths of an inch. If you use natural materials, you’ll get some variation in diameter anyway. One end of each tube needs to be closed off. (I did that with mud.) You need to have them set up so that you can either throw them away once they have been used, or sterilize them (e.g., soak in bleach) for re-use.
And you need to move your bee hotels (or the contents thereof) to a release box the next spring. That’s just a box with holes at floor level, so that the emerging bees will see the light and crawl out into the outdoors. That way, they can emerge, but they aren’t able to find their way back in again and re-use the old nesting tubes.
But, be aware that when they say you should try to attract bees to your vegetable garden, they didn’t mean mason bees. These guys are up and about way too early in the year to do my garden any good. They’ll have lived out their lives weeks before the first pea blossoms open up.
My upshot is that I need to let this box sit around for, at most, a couple of months. Then I can throw the whole thing away. I guess I’ll continue to put up bee hotels until I’ve used up my stock of six-inch bamboo tubes. But I’m not seeing any benefit to making this a permanent part of my garden.
Addendum
I relented. These are this year’s bee hotels, pre-mud. I took the best from my stash of potential bee nesting tubes. And tossed the rest.
My final thought on the emergence box is that mine is entirely in the shade. (Facing east-ish, on the north-ish side of the house, though I think that’s not very relevant.)
The point is, cool. Living in Zone 7b, with little nearby in the way of flowering fruit trees, I think the later my bees waken, the better. Within reason. There will be more around to eat, I think. In any case, no direct solar heating — no direct sunlight — is consistent with this year’s approach of not sheltering the bee hotels in winter. These bees are going to have to live in the ambient air. They need to be in sync with ambient air temperatures.
But I can see where, in a more northerly climate, you might make the other call, and at this time of year, if a bit of extra heat means having your bees up and about when their preferred blossoms are out, then that’s a good thing.
In both cases, I’m guessing that you up the odds of bee survival by trying to ensure that their emergence coincides with lots of local blooms, within what the bees themselves can tolerate.
Anyway, crocuses alone make slim pickings for orchard bees. My observation, based on my unfortunate experience last year. So perhaps I am erring on the side of caution.
Or, in this case, shade.
Epilogue: Psst. It’s the maple trees.
Why did this work well, in this location? Based on internet chatter, a lot of people have trouble attracting mason bees.
I did manage to avoid significant operator error, on my second try. This, by hanging the bee hotels in a sheltered place, then leaving them alone until it was time to move them to the emergence box in the spring.
But I think my success has more to do with the location, than with anything I did.
So, why is my back yard a good location for orchard bees?
Right at this moment, there’s little in the way of flowering trees in my area. (We’re in sync with the DC cherry blossoms, more or less.) I guess we have some Bradford pears out, but not in my area. My wife’s extensive daffodil beds are in bloom. But that’s about it.
Nary a blooming orchard in sight. It’s too early for most of the flowering trees in my area.
It was my pollen-sensitive wife who pointed out that there is one common tree that is flowering now: Maple. She knows these things.
And now that I look it up, yep, flowering maples provide food for orchard bees. So sayeth Google’s AI:
Arguably, then, my back yard is more-or-less mason bee heaven, owing to the presence of several large old maple trees. Plus mud, from the gardening. And nesting tubes, from the gardener.
Of which, the nesting tubes — nesting sites — were likely the “rate-limiting factor” in my local native bee population.
OK, let’s say this is all true. I could maintain an extensive population of mason bees in my back yard, owing mainly to the presence of several large maples there. As long as the mason bees emerge as the maples are flowering, the female bees have plenty to eat.
These bees still don’t do me one bit of good. In a food-production sense, these are not the bees I’m looking for, to pollinate what needs pollinatin’, in my garden. They are here, then gone, far too early in the year. (Further, my maples need no help in producing seeds, thanks.)
So there you go. At this point, I’m betting that this bee-wrangling went well, in my back yard, from the start, because mason bees can feed on maple flowers. Those are in abundance now. All these bees were lacking was nesting sites. And these hotels were the only game in town, or close to it.
But — aside from observing the great circle-of-life thing, as it plays out for the mason bee — it doesn’t do me one iota of good to maintain a mason been population in my back yard.
