Tag: mason bee

Post G24-004: Advice on sheltering your bee hotel for the winter.

 

My advice:  Don’t shelter your bee hotel for the winter.  Let it freeze along with everything else.  This post explains why.

Early bee emergence

Last year, for the first time, I hung up a bee hotel.  This is a set of nesting tubes designed to make it easier for solitary/native bees, such as mason bees, to reproduce.  It seemed to be quite successful, per the picture below.  Ultimately I ended up with about 15 nesting tubes filled.

I left that up through the summer and fall, and, per common internet advice, moved it to a sheltered location once winter set in.  In this case, I moved it to the inside of a detached, totally unheated garage.

Moving a bee hotel to a sheltered location, for the winter, is probably not a good idea.  Despite that being widely suggested by seeming experts.  That’s because if your sheltered area is even a little warmer than the outdoors, I think it entices the bees to emerge too early.

That’s what appears to have happened this year.  For my particular Home Depot bee hotel, the nesting tubes that were filled by mason bees last spring …

… are all now empty.

Consistent with that, my wife noticed some bees on her crocuses this morning.  Which was odd enough to stand out.  Because, among other things, not much is blooming right now except crocus and daffodil.  And it’s not all that warm out yet.  The upshot is that it seems a little early to be seeing bees out and about.

I’m betting that those were “my” bees.  And I’m betting that I did them no favors by (inadvertently) waking them up too early, this year.  If I put up a bee hotel again this year, I’m just going to leave it alone.  I’m now of the opinion that  bees ought to overwinter at exactly the temperatures they’ll face out-of-doors.

Like Tinder, but with only 15 people using it.

Experts say that mason bees should emerge when blossoms are open, and daytime temperatures consistently reach 55F (reference).

By those benchmarks — blooms and temperature — my bees are at least three weeks too early. That’s based on these observations.

Blossoms:  Slim pickings.  At present, only the crocuses, daffodils, and maybe a scattered other few species blooming.  There are a few cherry trees here and there, in this area, in blossom.  For reference, the earliest recorded peak bloom date for the national cherry trees is March 15, with April 1 being a typical date (reference March 15 to the National Park Service).  Separately, a harbinger of spring in many areas is forsythia, but our forsythia isn’t even close to blooming yet.

Temperatures:  Still too cold.  We’ve had a couple of days where the high exceeded 55F, but those are still few and far between.  We are not consistently 55F and higher.  But we’re closing in on that.

Source:  Weather underground. 

And based on our historical weather averages, you wouldn’t expect consistent 55F and higher days for another two-three weeks or so.

Source:  Analysis of NOAA weather data for Dulles Airport (Sterling, VA).

All of that, plus my experience last year, tells me that my little batch of bees emerged the better part of a month too early.  Call it three weeks, minimum.

Finally, these bees don’t live very long.  They emerge, eat, mate, and die within a span of a few weeks.  They’re now out of sync with their species in general, and they’re going to be dead before the rest of the local mason bee population emerges.  So, if they all survive, their procreation will be as described in the section title.

Conclusion

I’m not a bee expert, but I’ve spent a lot of time observing the habits of bugs, since I took up gardening during the pandemic.  The one universal rule is that everything in the garden — plants and bugs alike — operates on temperature, and on degree-days.

By keeping this bee hotel in an unheated garage, I kept it warmer than the ambient outdoor temperatures.  I suspect that, one way or the other, this caused my bees to emerge earlier than is optimal, for their species.

If I do this again this year, I’m going to leave the bee hotel outside all winter.  The bee larvae may not much like the cold, but they need to stay in sync with outdoor temperatures, in order to emerge at the right time.

Source;  All the pictures for this post are from Gencraft.com AI, with the prompt of “a bee, wearing a stocking cap and scarf”.

Addendum:  To bee, or not.

Edit:  In the end, I gave it another go, doing it better this time, as explained in Post #G24-008.  This year, my bee hotels are ugly, but properly constructed (closed-ended tubes roughly 6″ long), as shown above.  Well over half the tubes are now filled, as of this writing (4/22/2024).  I’m just going to leave them be until its time to take them down and put them in an emergence box next spring.

Original post follows.

Am I going to put up bee hotel this year?  Not sure, but at this point, I’d say, no not.  Probably not going to put up another bee hotel this year.  For the following reasons.

First, these bees don’t pollinate my garden.  They’re out and about early in the year, and they are gone by the time my garden crops or flowers need pollination.  So when you hear about “attracting bees to your garden to get better yields”, they ain’t talking about mason bees.  The earliest-blossoming food I grow is peas, and my recollection is that mason bees do their thing well before (e.g.) the peas blossom.  Apparently they are good for orchards.  Which would make sense, as fruit trees blossom early.  (And mason bees are orchard bees, or orchard bees are mason bees, or something, I’m not entirely sure.  I don’t have an orchard.)

Second, I’m trying to grow the kinds of plants that (the internet tells me) make good natural nesting sites for these bees.  But that whole enterprise is looking a bit sketchy at the moment.  I’ve started down that path, by not mowing my wildflower beds yet.

You’d think, well, that’s got to be dead easy, just grow some plants and leave them. Just don’t mow.

But its not that simple.

Mason bees need medium-sized hollow stalks to nest in.  (Or equivalent.)  That seems right by my experience so far.  Sturdy annuals will sometimes leave behind big, ugly stems.  Looks about the right size.

But that’s the point where anything ceases to be easy.

In a nutshell, you have to keep them for two years, they’re ugly, they get in the way, and you have to defend them from the deer.  I’m not going to go through the details.  I can boil it down to this.

Do I really want to use my time and attention to try to protect some ugly weed stalks from ravenous end-of-winter marauding deer?  For a couple of years, yet (the literal same batch of stalks, I mean.)  And somehow work around them, while prepping the beds for this year’s flowers.  And in the end, really have no clue whether they are effective or not.

I have a lot of sunk cost in this whole bee-hotel thing, not in the sense of buying the Home Depot wooden bee hotel, but mostly in the time and effort gathering and cutting bamboo, in anticipation of annul replacement of the nesting tubes in that hotel.

In addition, rehabbing that Home Depot hotel for re-use could be a fair bit of work.  I should replace the bamboo nesting tubes each year.  This year — with the off-the-shelf unit — that means breaking the existing glued-in tubes out first.

I think I’ll see how hard the rehab is, first, then decide on next steps after that.

But as of right now, I’m not seeing a huge benefit to anybody or anything in being a mason bee hotel keeper for another year.  I should let them find their equilibrium vis-a-vis the local flora.  Might tweak the flora to try to help them out, if I can figure out how to do it.  But I think I’m going to punt on maintaining a manufactured bee hotel.

Post G23-013: Bee hotel success, Part 1

I try to maintain a reasonably bee-friendly property, out here in the wilds of Northern Virginia.

It’s not just that I need them to pollinate my vegetable garden. Or that bumblebees do, in fact, sleep in squash blossoms (aw!).  Or that the hum of bees at work in my garden marked the never-to-be-repeated peak of mid-pandemic suburban quiet (Post #G11).

It’s more bee-as-coal-mine-canary. If I’m doing something in the yard or garden that’s likely to be killing off my bees, odds are I shouldn’t be doing that.  It’s a quick way to rule out some environmentally stupid behavior.

In any case, I’ve had a couple of bee hotels (native bee nesting boxes) kicking around my yard for a few years now.  Shown above.  But those were never very successful.  It took years to get the first bees to use them.  And I might get a one or two tubes filled, per year.  There are clear exit holes on some tubes, so some new bees were produced.

But not a big hit, over all.

This year, on a whim, I bought a different model of bee hotel, at my local Home Depot.  The Home Depot mason bee box is already working vastly better than the previous model.  It’s been up a few days and I already have more tubes filled than I got in the first few years of the other model.  In short, my bees love this new bee hotel.

Now that I’m finally doing something right, I’d like to keep that going.  In a radical and very un-guy-like step, I actually read the directions.    And — surprise — I’ve been clueless as to how these things actually work. 

But now that I know, I realize this new bee motel is a fundamentally terrible design.  Not for what you can see — that part’s OK.  And, as noted, it’s definitely attracting bees.  The problem is that those bamboo tubes are permanently attached.  As discussed below, that’s a no-no.  You want nice clean new nesting tubes each year.  And that means that, unless I tear it apart next year, this lovely little bee hotel is a single-use disposable item.

So this post is going to summarize everything I think I learned about mason bee nest boxes (“bee hotels”).  And about the difficulty of making smooth-ended splinter-free replacement tubes for this, from bamboo I have on hand.

Three-minute tutorial:  Bee hotel or roach motel?

Key point: For best results, you need two bee hotels (or equivalent) for every site at which you wish to maintain a bee hotel.

You ideally want the female bees to use clean, new nesting materials each year.  The use of new (or carefully sanitized) nesting tubes each year minimizes the presence of diseases and parasites in the nest.  If you don’t keep the premises clean, your bee hotel can end up as the bee equivalent of a roach motel.  With poor enough conditions, the bees check in, but they never check out.  Your bee hotel becomes a catch-and-kill trap. 

The problem is that each spring, some bees are ready to check into your bee hotel before your existing guests have checked out.  Some are ready to lay their eggs before others have emerged from their cocoons.  The reason for this chaos is that these bees are quite short-lived.  The emerge, mate, forage for food, lay their eggs, and die, all in the course of a few weeks in the spring.

The solution is to put last year’s bee hotel (or, at least, the nesting tubes) aside in an “emergence box”, to give the bees time to emerge from their cocoons.  At the same time, you need fresh, new nesting tubes nearby, for the emerging bees to lay the next generation of eggs.  An emergence box is just an opaque weather-protected box with a small opening.  This allows the newly-emerged bees to exit, but prevents bees outside the box from seeing (and therefore attempting to re-use) the old nesting tubes.

No matter how you cut it, you would ideally have two sets of nesting tubes in rotation at each bee hotel site.  One set of clean, new tubes, for this year’s eggs.  And last year’s tubes, from which bees continue to emerge.  You want to keep the emergence box with last year’s nesting tubes near your new bee hotel, because, as noted above, the bees get right down to business as soon as they emerge.

Here are my five Ws for bee hotels.

Who?  These bee hotels provide nesting places for some species of solitary bees, that is, bees that don’t form big communal hives.  Mainly, that means these are NOT for honeybees.  The bees that use these devices are typically referred to as “native bees”, but that’s imprecise.  For one thing, bumblebees are typically native bees, but those are ground-nesting bees, and won’t use these tube-type bee hotels.  Your primary target bee is a “mason bee”, so called exactly because they build those little mud walls at the end of the nesting tube where they’ve laid their eggs.

What?   A bee hotel provides tubular structures into which a mason (or similar) bee lays eggs.  The bee lays a series of eggs in the tube, providing each with food, separating them with mud walls, and capping off the tube with more mud.  Over the course of a year (in some cases, two years), each egg hatches into a larvum (worm), eats the food that its mother left for it, pupates (cocoons itself), and eventually emerges from that cocoon, the subsequent year, as a bee.

When?  The eggs are laid in spring.  The eggs hatch/larvae emerge in summer.  They cocoon in the fall.  And they re-emerge as bees the next spring/summer.  (In some areas, there are species that spend two years in the cocoon, but I’m not sure how relevant that is to most places.)

Place your bee hotel outside in the spring.  It appears to be fairly important not to disturb this during summer, as the larvae are delicate.  That means you attach it to something solid in the spring, so it doesn’t shake around, and you leave it alone.  The larvae pupate in fall.  At that point — late fall, early winter — they are tough enough to be moved.  Place the bee hotel in a sheltered, unheated location (such as an unheated shed).  Then, next spring, place the bee hotel (or the tubes from it) in an “emergence box”, move them back outside, and let the bees emerge as the weather warms. Google “emergence box”, but it’s basically a sheltered box with a hole in it, to let the hatched bees escape.

Some experts “harvest” the cocoons as an extra sanitation measure.  They break open the nesting tubes, remove and possibly clean the cocoons exteriors, and place the cocoons in fresh material for eventual hatch-out in the spring.   The claimed advantage of this is that it separates the bees from various parasites that may linger in the nesting tubes and this allows them to emerge from overwintering parasite-free.  If you are going to do that, you need to use relatively fragile nesting tubes (paper liners, reeds) that allow the cocoons to be removed undamaged, and not sturdy ones such as bamboo tubes shown above.

As of this writing, it’s not clear to me how much of an advantage you gain by harvesting cocoons, or what evidence basis there is for it.  The only obvious advantage is that if certain fungal diseases are present in the nest, you’ll see them if you harvest the cocoon.  As I plan to use all-new materials each year, I’m not sure that’s much of a concern to me.

Where?  These bee nests ought to be protected from rain, protected from getting cooked in the afternoon sun, and so on.  he most common advice is to locate them to catch morning (but not afternoon) sunlight.  They need to be firmly attached to something substantial because the larvae are delicate and don’t want to be tossed about.  In plain sight, so the bees can find it.  And near a ready source of mud.  Because bees need mud to cap off their egg cells.

Upshot:  Facing east-ish, under eaves if possible, firmly attached to something, near water or mud, maybe 5′ off the ground, and plainly visible.

Why and how? Different bee species want different sized tubes.  So from the get-go, a rack of identical tubes limits the species that can use that particular hotel.   The tubes need to be closed off at the back, in some fashion.  The tubes need to be sturdy enough to keep out various bee predators.  Paper straws alone, for example, appear to be frowned upon, thought to be too fragile to keep out certain types of bee predators.  In rare cases, you need to put hardware cloth across the front to keep birds from pecking out the larvae.  That’s only necessary if you wake up one morning and all the previously-filled tubes appear empty.

The simple upshot of all this is:

  • Each Spring, put last year’s nest out in an emergence box.
  • Nearby, place a clean, new nest out to attract bees.
  • Each Fall, refurbish last year’s nest, to be placed out the next spring.