Mason Bees; North American Native Pollinators


We’ll be lucky to get any Osmia lignaria bees this season as they generally try to already have a nesting site by now. They are a very early season pollinator!

However, there is a second native bee that may likely take up residence and provide effective pollination services all summer. Osmia californica, another mason bee, takes over about the time lignaria is done!

I might order some tubes of Osmia californica bees to kick start the local population.

Ready for Occupancy!

If you have any interest in gardening or flowers, or follow any kind of agricultural related financial markets, you are likely aware that one of the ecological disasters we face is known as colony collapse disorder.

Basically, the worker bees in a honey bee colony die, get lost, or otherwise just cease to function. The cause has been attributed to pollution, mites, genetic degradation, pesticides, genetically modified crops, and/or a slew of other guesses.

It is a serious problem in that bee driven pollination of crops is what sustains much of the agricultural production in the United States.

Oddly, though, the european honey bee — the bee that everyone immediately thinks of as the One True Way that flowers are pollinated to yield seeds and crops — is actually an imported species and, frankly, a bit invasive at that.

Not only invasive, honey bees tend to be territorial in that they will actively defend their hive. As well, they really aren’t even that efficient as pollinators.

Not surprisingly, there are many native pollinators buzzing or flitting about. In the South Bay, the most noticeable are the carpenter bees as they are gigantic, relatively clumsy, totally non-agressive, fuzzy, and have a noticeably loud buzz while flying.

But they aren’t the true superstars of the native North American pollinators. For that, one should look to the Mason Bee or Orchard Bee (Osmia lignaria).

The mason bee is a rather docile flying insect that is considerably smaller than the carpenter bee. Like the carpenter bee, it is non-territorial, won’t sting unless seriously threatened, and is non-swarming.

The mason bee is an extremely efficient pollinator as a single bee may visit over a thousand blooms per day.

Clearly, this is a bug whose presence should be encouraged!

Fortunately, it is easy to provide housing for such a helpful critter. Roger is standing next to a mason bee home that we made over the weekend. We chose to make one out of a block of wood. However, bundles of reeds, bamboo or — even — appropriately sized straws work quite well, too.

Gridmarked 4x6 Ready for Drilling

To make a wood based bee house, start with a block of 4″x6″ wood. Soft wood — fir or pine — works best and it must be untreated.

As the nesting holes need to be at least 4″ deep, you’ll be drilling into the 4″ side of the wood.

Draw a grid on the wood with the holes all being separated by approximately 3/4″.

Don’t worry to much about making the lines straight. The bees really don’t seem to care!

Drilling the 4x6

At each intersection, drill a 5/16″ or 3/8″ hole that is at least 4″ deep, preferably about 5″ deep (no more than 1/2″ from all the way through).

Hole diameter and depth is rather critical. Any narrower or any shallower and your bees will tend to produce male offspring. The male mason bees don’t live as long and are not terribly good pollinators, by comparison.

A drill press — especially one with lasers — definitely makes this particular part of construction go much much faster!

Finished House with Roof and Mounting Holes

Once drilled, I also sanded the front face of the house. Not so much because I was worried about the bees getting splinters, but because the wood was soft/wet enough that some of the holes had been a bit blocked by wood after drilling. Thus, sanding opened the holes a bit.

Fit a bit of scrap wood on top of a make shift roof. It doesn’t need to hang over that much. The roof exists mostly to provide a bit of early afternoon shade and to shield the front from water running down it during rain.

If you want, you can stain the outside, but not the nesting holes, obviously.

Mount your mason bee house with a South-SouthEast exposure. It should be at least 3 feet off the ground and should be exposed to the morning sun as the morning warmth encourages the nesting bees to get out and get busy.

Simple enough. I’m not sure we put our houses out early enough in the season. We’ll see. If not, there is always next year!

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10 Responses to “Mason Bees; North American Native Pollinators”

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  3. Jeffrey J Hoover says:

    An awesome post to discover on Earth Day! Thanks bbum!

  4. annbb says:

    Why isn’t the mason bee more heavily promoted? I keep on read that when the honey bee population is
    gone, we have just a short time left on earth…wouldn’t mason bees just take over?

    I agree with Jeffrey – perfect Earth Day post! And a great pic of my Dodgie.

  5. John C. Randolph says:

    Will the bees re-use those same holes the following year?


  6. James Fischer says:

    Saw your comment over on Ethicurean, and noticed that you were parroting a number of mis-statements about solitary bees versus honey bees.

    So, I’ll cut an paste some FAQ fodder as answers to some of your claims to help get you up to speed:

    > To preserve the honeybee in North America is to preserve an invasive species.

    Native bee advocates should not demean honey bees with their mouth full. 🙂
    Honey bees are not “invasive” they were and are “introduced”.
    The European honey bee is adapted to be the best pollinator of all the introduced vegetable and fruit plants and trees that provide about 1/3 of our diet.

    The general rule of thumb is that the pollinator must be adapted to the bloom, and if the plant is introduced, you can’t expect a native pollinator to be a very effective pollinator of an introduced plant, can you?

    > There are very effective native pollinators throughout the Americas,
    > many of which have been pushed out by the honeybee.

    This is misinformation. There is no evidence at all of “competition” between honey bees and any of the so-called “native pollinators”. Most of the native pollinators are focused on very specific lists of non-food plants, and will not gather pollen from any other plants. These specialized pollinators do not exist where the plants do not exist, so it is an issue of environmental preservation, not “competition”.

    Native bees collect pollen and nectar for one egg at a time, and have very limited flight ranges, in some species only a hundred yards from their nest. They simply cannot be expected to provide the amount of pollination required for the large orchards and large plantings that are common in modern agriculture. They will do just fine for a small backyard garden, which is where we deploy them.

    > These native pollinators are often more efficient than honeybees

    People repeat this fable all the time, yet the amount of pollen gathered by native pollinators is a tiny fraction of the amount brought in by honey bees when one compares bee to bee payloads. When one realizes that a single honey bee hive can make hundreds of sorties per minutes, versus one sortie every few minutes for a native pollinator, one sees just how powerful a pollinating force a single honey bee hive can be, which is why it has been the only pollinator man has been managing for 3000 years.

    > are generally considerably less territorial and/or aggressive,

    Honey bees are not aggressive at all. Yes, they will defend their brood and food stores if you disturb their hives, but otherwise, you can put a lawn chair next to a bee hive and sunbathe if you’d like.

    > providing better full-season coverage than honeybees.

    More nonsense. Honey bees can pollinate whenever they can fly, and they can fly whenever the temps are above 50 or so. Solitary bees do about the same, but only live until the end of July or so, hatching out again in spring just about when the fruit blooms start.

    > For this season, I built a Mason Bee house for my community garden plot.

    We deploy paper-in-cardboard tubes in PVC enclosures for Mason Bees like this:
    They can be very effective for small garden plots, but less so for gardens over an acre. A good basic book you should read is “The Mason Bee” by Jean-Henri Fabre. The behaviors he describes are common to nearly all types of Osmia.

    You do need to work out a way to protect the larvae from predatory wasps once the tubes have been sealed, so once the bees have died off (late July) cover the openings with securely-stapled window screen. You may want also to buy the paper tubes from Knox Cellars and use them, as over time, wood blocks tend to become infested with tiny mites that infest Osmia and the pollen they collect.

    See exclusive photos of the Obama’s White House Bee Hive here:
    Note that honey bees were chosen over Mason bees, as Osmia simply don’t do well East of the Rockies. Often, we have to use an imported species – Japanese Hornfaced Bees for some sites. Would you also call these bees “invasive”? Thought not. 🙂

  7. bbum says:

    James — thanks for taking the time to provide such a detailed counterpoint (which is a stretch because my original point was not nearly so considered as your post).

    I fully agree that calling honeybees invasive is both too simplistic and implies that they are a damaging species without acknowledging that the honeybee is often maintained to optimize the yields of the various non-native fruits and vegetables for the food production pipeline.

    There are actually numerous studies exploring competition between native pollinators and the non-native honeybee. The conclusions are generally that there is enough interaction for their to be some impact, but the details of the impact are unknown.

    While you are correct that the mason bees — both Osmia lignaria and Osmia californica — don’t live east of the Rockies, there are, quite literally, hundreds of other native pollinators throughout the Americas (apparently, Texas alone has about 500 species of native bee, not all pollinators, but many do). Some studies have shown that native bees in the eastern states — New Jersey, Pennsylvania, and New York, specifically — will provide 90% of the pollination capabilities of honeybees.

    There are also a number of studies that indicate that honeybees have a detrimental impact on the effective pollination of native fruit and vegetable plants. That the introduction of honeybees to support non-native fruits and vegetables is reducing the yields and, eventually, the presence of native fruits and vegetables.

    So, no, this issue is not as simple as you or I have portrayed it and, when I have a chance to actually grok the piles of research, I shall update the post. One of the immediate updates would be that native pollinators are definitely not sufficient for commercial level vegetable production (though it appears that fruit orchard farmers have been using native bees for quite a while — then again, many of the orchard fruits are derived from or close to native North American fruiting tree species) and, for that, the honeybee is currently quite critical.

    That should come as no surprise. Modern factory farms generally focus on vast expanses of relatively singular species, genetic monoculturues, even. This is about as unnatural of a plant growth habit as you can get. And to support that requires a pollinator optimized for such an environment, of which the honeybee is exactly that.

  8. annbb says:

    I always learn much more than I thought when I visit here.

  9. annbb says:

    And that’s good.

  10. Roxanne says:

    Wow, that is an easy way to start to be a pollinator. Too bad I’m allergic to bee stings. I can’t do this.

    [Ed: I love spammers that try to write something poignant only to miss the point entirely. Good job. Link deleted.]

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