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Bee gardening news and education from the UC Davis Bee Haven
by James mr McDonald
on March 4, 2019 at 7:08 PM
Reply by Christine Casey
on March 13, 2019 at 11:55 AM
Thanks. I've added an updated photo showing how the bee house fared over the winter.
by Jen
on March 7, 2019 at 1:01 PM
Hi! I have one of these but my model looks a bit different. A couple of the tubes have been “built in” with a white material. How can I tell if they are the solitary bees? Thanks :)
Reply by Christine Casey
on March 13, 2019 at 11:56 AM
Jen, only solitary bees will use these houses. If your tubes look like they have been filled with cotton, that's the work of the wool carder bee.
by John Bishop
on March 18, 2019 at 2:50 PM
What I do is take the plastic Costco packaging for apples. I cut it to fit and cover the roof. Basically, I just staple the plastic to the roof and I make the plastic big enough to put an extra 2 inches of plastic over the front.  
Last winter we had lots of rain (of course) and no rain messed up the bee house.  
Just an idea from a newbie mason bee aficionado
Reply by Christine Casey
on March 18, 2019 at 3:00 PM
John, sounds like a great idea; I'd recommend an even larger overhang. Depending on where you are located, the plastic trapping heat might be a concern. Just make sure that the bee house is out of direct sun in the afternoon, or you might want to remove the plastic all together once the rainy season is finished.
by William Marsh
on March 19, 2019 at 7:44 AM
Hi Christine and group. It seems Costco has re-designed their Alps model Mason bee house for 2019, so Christine do you have any updated comments. IMHO, the data/instructions regarding this new adventure for me (i have 5 fruit trees, 4 are just beginning to blossom) is pretty sparse: e.g. how to harvest the cocoons etc. Do these bees essentially do the whole process?? provide their own nurishment, seal themselves off and then make their way out in the Spring?
Reply by Christine Casey
on March 27, 2019 at 10:54 AM
I've not seen the new model in person, but from the pictures it looks similar to last year's. Still has nesting tubes of incorrect diameter that cannot be removed. It appears that they have added a space for butterflies on the top. Unfortunately the only study that I'm aware of found that butterfly houses were used mostly by spiders.  
As far as hosting cavity-nesting bees in your garden goes, the bees do it all. It may take a few years for them to find your nests, but once they do they tend to return in subsequent years.
by Leah
on March 28, 2019 at 2:50 PM
So glad to have found this! I was excited that Costco started selling something bee-friendly, and bought one, but haven't installed it yet.  
Is there a downside to having the larger openings/butterfly openings clear for spiders? Would they prey on the bees so they wouldn't come near the house? I don't mind keeping house for the spiders, but don't want to at the expense of the bees!
Reply by Christine Casey
on March 28, 2019 at 3:31 PM
There is a possibility that spiders or wasps might use the larger tubes or the gaps between the tubes. You could place the house and watch to see if this happens, or go ahead and cover the two side sections with wood or some other durable material. I'm going to leave mine in the garden as is and watch what happens.
by Matthew Ross
on April 26, 2019 at 9:36 PM
I purchased the Costco Bambeco barn. My bees are ONLY building nests in the bamboo tubes. Not a single one in the center removable blocks. Anyone else have this issue?
Reply by Christine Casey
on May 6, 2019 at 9:33 AM
There is nothing wrong with what you describe. I would take this opportunity to purchase and install paper liners for the center blocks. You'll be able to take the removable blocks out and continue to use them if they are kept clean with removable liners.
by Tara
on April 28, 2019 at 5:22 PM
I have the costco mason bee house and I'm wondering where to put the paper tubes(should I put them in the nesting trays?)....the bamboo tubes on the side are all different sizes and how would you get the bees out if they nested in there as they are glued in and you can't get into them
Reply by Christine Casey
on May 6, 2019 at 9:35 AM
If you have paper liners, I suggest placing them in the center removable wooden blocks. That way you'll be able to keep the center blocks clean so they may be reused. I don't recommend bee houses that have the nesting tubes glued in place as they cannot be replaced after use.
by Christy smith
on May 5, 2019 at 7:55 AM
I also just bought the Costco bee house but upon further reading have more questions. First being the length of the tubes- another resource mentioned they should be at least 6 inches long.  
Secondly, I keep reading that the mason bees can more successfully find their tubes if the tubes are irregularly placed (the bamboo configuration,) however, then i read that most of the bamboo tubes are incorrectly sized. Which brings us to the manufactured blocks- correct size, but not at irregular intervals. So which is better or worse?  
Third, I'm confused about the "har vesting" of the cocoons; the costco directions say to overwinter the whole house but other sites talk about removing the cocoons from the tubes, and if you are doing that, then it's very difficult to remove them from the bamboo tubes and instead should use the easily dissasembled block configuration.  
Not sure what is the correct or best information to use. Thanks.
Reply by Christine Casey
on May 6, 2019 at 9:43 AM
To answer your questions:  
1. Nesting tubes should be 4 to 6 inches long.  
2. There is no right or wrong configuration. We recommend a nest with varied tube diameters (correct sizes are 3/16, 4/16, and 5/16 inches across) to attract a variety of bee species.  
3. There is no need to harvest cocoons; the bees emerge on their own. It is a good idea to keep the bee house in a protected, unheated area over the winter. As you can see from my post, the wood of the Bambeco bee house did not hold up well over the past winter. An unheated garage works as a storage location; at the Haven we place ours inside buckets that are kept outside.  
For more information, I did a blog post a few years back about using solitary bee nests (, and we have a fact sheet on our web page (
by Diane
on May 7, 2019 at 6:21 PM
Will this bee house work for leaf cutter bees in the center block with the tube inserts? I ordered cocoons but am not sure where in the bee house to put them. I'm thinking of cutting the face off the part that is reserved for butterflies and putting the cocoons in there. Thanks for this great article and thread. It is very informative.
Reply by Christine Casey
on May 8, 2019 at 8:27 AM
I don't see this house working for purchased cocoons.  
First, as you realized, there isn't a good place to set them in the house. Removing the face of the butterfly section might work if your cocoons arrive already harvested, but not if you receive filled tubes.  
Second, bees tend to return to where they emerged to nest. Given the flaws in the design of this house, I'd not want to encourage that.  
FYI, here's a good video that explains the process of releasing cocoons:
by Daniel Fay
on May 9, 2019 at 5:30 AM
Hi Christine, my daughter (kids!!) says I need to remove the back of the mason bee barn, for air flow, but I cannot find anything on this, any thoughts? Thanks - Dan
Reply by Christine Casey
on May 9, 2019 at 1:16 PM
Your daughter is incorrect. The back of the bee house MUST be solid....if bees can see light through it they will not use it.  
It's helpful to remember how they nest in the wild. They use cracks and crevices underneath tree bark, such as those excavated by beetles. These certainly have no air flow.
by Diane Clayton
on May 11, 2019 at 3:55 PM
The leafcutter cocoons will arrive harvested. The back of the bee house has a small circular opening with a movable tab to open and close the opening. I plan to put the cocoons in the butterfly housing through the rear circular opening. I kept the front butterfly panel on but widened the top of the butterfly slats just slightly so the bees can get out. Can you tell me what diameter the opening in the butterfly panel should be so the bees can get out? Basically all I did was drill a hole just slightly wider than the diameter at the top of the butterfly slot. (The slots are now the shape of matchsticks.)  
After we put the cocoons in the butterfly housing through the back opening, and hang the house back on the post, they only way the bees will be able to get out is through the butterfly slot. I want to make sure it is large enough. Also, I'm thinking that I will close the rear circular opening once the bees are inside. I'm not sure that it makes any difference but appreciate your input.  
I will have the pheromone from Crown Bees to add to the tray so encourage the leafcutters back to the house. I took the reeds out of the house and will save for mason bees next year. I only have the center trays in the house and will close of the side panels where the reeds were. I also extended the roof by 2.5 inches to give the bees more shelter.  
The leaf cutter bees should get morning sun but not afternoon sun? Correct? Is there any danger that the morning sun is too strong? I am going to build a shade barrier for the afternoon sun but not sure if I should do the same for the morning sun.  
Thanks again for all your help. Your post is informative.
Reply by Christine Casey
on May 15, 2019 at 12:33 PM
The leafcutter bees will be able to escape through the openings meant for butterflies. The recommended diameters for leafcutter bee nests are 3/16, 4/16, and 5/16 inches. Morning sun is fine, but in hot climates like the Sacramento region afternoon sun should be avoided.
by Diane Clayton
on May 15, 2019 at 5:22 PM
Thank you.
by Javier Gil
on June 11, 2019 at 4:12 PM
I bought Bambeco Mason Bee Barn at Costco. There an opening in the back of the house that can be opened, however if you mount on the fence nothing will be able to enter, most examples I have seen with this type of house call for mounting on a fence or wall. Please advise what do with opening, keep open?
Reply by Christine Casey
on June 12, 2019 at 5:09 PM
I'm not sure what you're referring to, as the bee house I have is closed in the back. There is a keyhole cutout for mounting on a screw or nail. Bees will not use these types of nests if they can see light through the tubes, so if that's the case with your house the opening should be kept closed.
by Mimi
on June 18, 2019 at 5:53 PM says in the instructions to bring it into a shed or some place to winter over.
Reply by Christine Casey
on July 1, 2019 at 9:55 AM
The overwinter location for cavity nesting bee houses will depend on the amount of protection the bee house has. If it's in a protected location, for example under the eaves of a building, it can likely stay in place.  
If it's in an area subject to regular rain and there is no overhang protecting the nesting tubes (as is the case with the houses I've reviewed), it would be good to bring it into an unheated building. At the Haven, our houses are protected by an overhang but are subject to squirrel predation. I place all bee houses in a large lidded bucket that is kept in an outdoor storage area over the winter.
by Michael Beneke
on July 22, 2019 at 6:30 PM
Within a week or so I had nests in the bamboo sections of the Costco Bambeco Bee House and nothing in the block housing. Wild flowers bloomed all around the vicinity and I have drip feed water for the bird bath nearby, but for the next three months no activity. I now realize I placed it on a fence facing west...hard afternoon sun. The new location will bee under an eave of the house and about 8 ft high. On the North face of the home I have a security motion detector about nine feet up and in the screw holes holding the housing together (about two inches depth) all are filled with bee nests. So I'm guessing it doesn't much matter to them which direction they face as long as they are not cooking in the heat of the day and have an overhang.
Reply by Christine Casey
on July 23, 2019 at 4:44 AM
Michael, glad to hear you've got nest activity. You are correct that some type of shade is one study simply draping burlap over the top of the nest block was enough to make a difference. In terms of direction, just be sure not to face the openings into the prevailing wind.  
Since the bamboo sections of the Bambeco house are not removable, you'll need to discard your house after the bees emerge next spring. You'll notice that the center block is removable, so you can pull that out for use without the house.
by Cathie
on July 28, 2019 at 2:19 PM
My problem is that the bees have pretty much filled the irregular bamboo tubes and I do not understand how to get the cocoons out without harming them
Reply by Christine Casey
on July 29, 2019 at 10:08 AM
If you wish to harvest cocoons, you need to use a special type of cardboard nesting tube that is designed for harvesting. There is generally no need to harvest cocoons in a garden, as they will emerge on their own next spring.
by tom
on September 15, 2019 at 9:25 AM
OK, I like the conversations at this site; many have been helpful, however, i just want to know the "BEST" things to do, and materials to buy (and where), which will encourage and protect the 'BEST' pollinators.  
I am in Sparrows Point, Maryland and just placed those houses in mid summer and only now (15 Sept.) the tubes are being capped at the rate of about two per day.  
I have three Costco Bambeco Bee Houses placed at various locations throughout my yard/garden.  
Also, is there something i can do to reduce the number of spiders and ants that seem to be attracted to the nesting tubes?  
Thanks in advance for your help.
Reply by Christine Casey
on October 7, 2019 at 12:55 PM
Please see the comments and photo I posted today, October 7, 2019.
by Sophie Belanger
on September 21, 2019 at 5:57 AM
Quite a few of the holes are plugged.  
I am living in Montreal Canada and just ensuring that placing the house in a lidded bucket in the shed, when the temperature can dip -30 Celsius at some time during the winter is still reasonable?  
Also trying to understand when do I return the house to its location (when the nights no longer dip below what degree celsius).  
Reply by Christine Casey
on October 7, 2019 at 1:06 PM
Glad your bee house is being used. The bee house should be kept in an unheated area over the winter...remember that the bees in your area are adapted to your low temperatures. You may return it to its location when it's mostly finished snowing, probably around mid-May.
by Suzanne
on October 2, 2019 at 9:25 AM
Hi Christine, thank you so much for such a great post and answers, I am sure I can speak for all in saying we really appreciate your help and sharing your knowledge.  
We have one of the 2019 Costco models of the bee house and are planning to put it up this coming March (we live in Northern Virginia). Of the noted issues, I got mostly concerned with the mold issue you ran into. Would it be detrimental if we were to use a coat of protective finish such as polyacrylic to help prevent moisture from building up in the outside of the house?
Reply by Christine Casey
on October 7, 2019 at 1:08 PM
Please don't apply any protective coating. This could trap moisture inside the house and lead to rotting of the nests.
by sarah peebles
on November 12, 2019 at 2:39 PM
Hello. I'd like to add that there is no one 'correct' way to build a bee house for solitaries. I've created a page about DIY houses with maintanance, biology etc. It's important to note that in having these bee houses, our aim here is to cultivate our understanding of bee and wasp biodiversity, of their roles in ecosystems and agriculture and of how ecosystems support solitaries. We’re not especially helping solitary bees and wasps by making hotels, but our hotels can inspire us to cultivate landscapes which self-generate structures found in nature so that they may thrive. More at Resonating Bodies: . Thanks, Sarah in Toronto
by Nurzhan
on February 26, 2020 at 9:06 AM
Thanks for the review of the Costco one. I tried to find the log bee house that you mentioned that you sell at Haven but I can't find it. I would like to buy one, where should i look?
Reply by Christine Casey
on March 2, 2020 at 11:20 AM
I'm not aware of any sources for bee houses like we sell at the Haven. We'll have them available at our next open house on March 21, 2020 from 10 to 1.
by Tracy
on June 15, 2020 at 6:19 AM
My daughter received the Costco Bee Barn as a gift. We set it outside amongst lavender and zinnia. There is a bush close by with small white flowers that attracts bees. After 2 weeks there still are no bees on the bee barn. Any suggestions? We are totally new to this but want our daughter to learn about the need for pollinating bees.
Reply by Christine Casey
on June 15, 2020 at 8:43 AM
It's great that you're teaching your daughter about bees. Two weeks is a very short time to expect a bee house to be used. The solitary bee house isn't like a honey bee hive that will be immediately populated. It can take several years for leaf cutter bees to choose a particular nesting location. The good news is that once they use a nesting location they tend to return to the same area.  
You might also not have the bee species that use the solitary bee house. These are used by leafcutter bees, which can be distinguished by the fact that they carry pollen on the underside of the abdomen and not in pollen baskets on their legs.
by Tim Pelican
on July 4, 2020 at 8:00 PM
If one lives in a fairly mild winter climate such as the northern San Joaquin Valley in California is it necessary to store the house in the Winter?
Reply by Christine Casey
on July 6, 2020 at 6:34 AM
No matter the climate in which a bee house is used, the bees in an area are likely adapted to its winter temperatures. The purpose of storing the house in the winter is to keep it dry and prevent rotting of the bees inside.  
At the Haven we place our bee houses in a covered bucket that is kept outside.
by Jason
on August 15, 2020 at 5:21 PM
We bought the 2019/2020 model at Costco. We hung it on tdd the wall of our garage, facing east, under the overhang of the garage.  
The bees are using the side tubes, and not the center tubes. 4 were capped off in late spring/early summer with clay/dirt. In the last 5-10 days another 10.holes have been capped off with leaves, and a few more are in progress.  
It's still in great shape, and I'm pretty pleased with it overall. But I can see that if I hadn't put it under a deep overhang, or faced it East, it may not have worked as well.  
I also planted a rose bush directly under it, and left some of the clayey soil from the hole I dig mounded up where the bees could get to it.
Reply by Christine Casey
on August 18, 2020 at 1:13 PM
The center tubes in the Costco house are mostly too large for bees, so I'm not surprised they are not being used. I hung mine on a pergola post with no protection and it fell apart after one year. Please remember that since the used tubes cannot be removed for replacement you'll need to discard this house after another season.  
Some mason bees may use the soil you dug up. Ground nesting bees tend to use native, undisturbed soil.
by Marc
on April 17, 2021 at 8:29 AM
Jai un problème à chaque saison un pivert passe dévoré toutes les larves :( des suggestions?
Reply by Christine Casey
on May 5, 2021 at 10:28 AM
Je suis désolé que vous rencontriez ce problème, malheureusement ce n’est pas si rare. Les abeilles ne placent que des œufs mâles à l'avant du nid car elles ont évolué pour subir une certaine perte par les oiseaux. Cela protège les œufs femelles les plus précieux.  
Je recommande de placer du treillis métallique sur le devant de vos nids. Sélectionnez un maillage avec une ouverture assez grande pour que les abeilles puissent passer à travers à mesure qu'elles émergent, mais suffisamment petite pour empêcher les oiseaux d'entrer.  
Translation: Marc is having a problem with woodpeckers damaging his bee nests to eat the developing bees. This is not unusual, and bees have evolved with this damage and place the more expendable male bee eggs at the front. I recommend trying to cover bee houses with wire mesh that will allow bees to exit but prevent birds from reaching the nests.
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