Tag Archives: wood

Guide to building mason bee houses

DIY bee hotels can be filled with (1) routered nesting trays (with our without with paper inserts), (2) drilled wood blocks with paper inserts, (3) drilled wood blocks without inserts, or (4) hollow stems. Or, like house in the photo below (construction details here), all four types — each type has pros and cons.

The key is to build the hotel so that everything can be removed to make room for fresh nests each year. I.e., you replace everything except the house itself. Note: you can reuse drilled blocks of wood (or sections of logs) if you re-drill them (to remove debris) and then kill any residual mites and pathogens by briefly submerging in bleach (or baking, or freezing). Similarly, nesting trays should be cleaned and sterilized (Crown Bees has nice video of that).

Below are some links to houses I admire.

If you’re lazy but want a mason bee house ASAP, just buy one. Here’s a draft listing of companies that make good mason bee houses. Here’s a guide to avoiding death-trap bee houses.

Questions?

Or just want to show off your mason bee house? Email me.

If you post your house pic online and want to tag me, I’m @colinpurrington on Twitter, @colin_purrington on Instagram. If you want to see pics of all the beasties that show up at my mason bee houses, I have them all on iNaturalist.

Where to buy mason bee houses

The following companies or individuals sell bee houses that have 6″ (152 mm) nesting holes, have disposable or cleanable components, have protective roof overhangs (usually), are not suspended with string, and do not use bamboo. Some of these sites also sell cardboard and paper inserts, routered nesting trays, etc.

  1. Bee Built
  2. Beediverse
  3. Bee Foster
  4. Buzz Heroes
  5. CJ Wildlife (UK)
  6. Crown Bees (has excellent newsletter, Facebook page, Instagram)
  7. Farmstand Supply
  8. Forest Flower Shop
  9. Grass Roof Company (UK)
  10. Good Riddance Farm
  11. Healing Farm
  12. Hive and Garden
  13. JC’s Wildlife
  14. Kinsmen
  15. Knox Cellars
  16. MasonbeesUK (UK; check out their tube exchange program)
  17. Mason Bee Central
  18. Mystery Seller
  19. Nurturing Nature (UK; has great blog, too)
  20. One Green World
  21. Osmia Bee Company
  22. Park Seed
  23. Pollen Bee Nest
  24. Potting Shed Creations
  25. Rock Pond Nursery
  26. Territorial Seed Company
  27. Two Bees Apiary
  28. Welliver Outdoors
  29. West Coast Seeds
  30. Windowbox
  31. Woodlink

If I’ve missed somebody, send me a note and I’ll update this post.

Here’s a guide to avoiding death-trap bee houses. If you’re handy, you can also make your own.

The horrors of mass-produced bee houses

Here are some reasons why cheap mason bee houses can end up hurting bee populations.

1. Nests are too shallow

The house pictured above is approximately 2″ deep, far too short to actually help bee populations. In nature, mason bees lay fertilized eggs (which develop into females) at the backs of long nests, then pack the front with unfertilized eggs (which develop into males). This means that houses with short nests end up being nurseries for worthless guys (sorry, guys). If you want a house that can generate an ecologically useful proportion of females, only buy houses with nesting tubes that are approximately 6″ (152 mm) or longer. That rules out almost all houses on the market these days.

2. Nesting blocks, tubes, reeds are not removable

Mason bee hotels can quickly becomes feeding troughs for dozens of species of parasitic wasps and flies, kleptoparasitic mites (they eat the pollen, image below), and various fungi and bacteria.

Hundreds of Krombein’s hairy-footed pollen mites on a mason bee. Image by @GeeBee60.

So you absolutely have to empty out the house every year and give it a good cleaning. And during the winter the filled nesting tubes or blocks should all be stored in a safe, unheated garage or shed. And then in the early spring, those nests should be placed inside a cardboard box that is equipped with a small exit hole — so bees can escape but can’t re-inhabit the nests. Once everyone is emerged, clean the trays (brush, bleach), re-drill holes, and throw away reeds and paper tubes. While all this is happening, you will need to equip your cleaned house with fresh nesting trays, blocks, paper tubes, reeds, etc. All of this can’t happen, of course, if everything is glued in place.

If the above sounds like way too much maintenance, don’t buy a mason bee house. Get a garden gnome or a gazing ball.

3. Roof lacks overhang

Mass-produced mason bee houses are designed to be as compact as possible so they can be packed and shipped efficiently from factories in Asia. This usually means that they won’t have roofs that protect the nest entrances from water. That’s bad, especially in rainy climates. Moisture causes larvae to rot and also seems to cause kleptoparasitic pollen mites to flourish (that’s bad).

4. Nesting material is impermeable to water

Like anything that’s alive, mason bee eggs, larvae, and pupae produce water from respiration. When that moisture can’t escape the bees will become susceptible to bacterial and fungal pathogens. So avoid houses that use bamboo, plastic, and metal tubes. Yes, bamboo is pretty much impermeable to water when mature. You want, instead, paper/cardboard tubes, hollow stems, or holes drilled in wood.

5. House attaches to tree with string or hook

Mason bees start their lives as eggs on top of a mound of pollen, and houses swinging in the wind can cause them to fall off. Starving to death so close to a bed of food is a terrible way to die. Also, mason bees have difficulty landing on a moving house. Only get houses that attach to walls with screws.

6. Nesting tubes open at back

If holes aren’t capped in some way at the back, parasites can easily gain entrance. Mason bees will plug the back with mud but it’s best to have a wall.

7. Reeds or holes with large splinters

Sharp edges inside the holes can snag and tear delicate wings.

8. Stems blocked at front

In the majority of houses that use bamboo, a good proportion of the sections are blocked off near the front by a node. This is just another sign that the makers of the mason bee house could care less about bees.

9. Too many nesting units

When thousands of mason bees are living in close proximity, parasitic insects and mites can easily find every nest. Just like bed bugs in a large hotel. If your heart is set on a mason bee mega-complex, just be extra sure that all components are truly cleanable or disposable. It’s also critical to actually clean it, too, so don’t buy it if you’re the type that doesn’t like to do that sort of thing.

These look soooo cute, but if ALL the blocks are left in place for multiple years they become towers filled with bee parasites.

10. Honey bee shown on packaging

Companies that don’t know what a mason be is shouldn’t be selling mason bee houses. It’s a sure sign that the house is not up to code.

Mason bee house with honey bee drawing

Flow chart for making buying decision

Here’s a summary flow chart to print and keep in your wallet so you’re prepared when you see something adorable. Or print and give to that shop owner who carries trap houses.

“OMG I own a death trap what should I do?”

If you have a cheapo mason bee house that saddens you, don’t do anything rash. Just leave it up and let your current residents do their thing. But at the end of the season, after all the holes are filled, put it in an unheated shed or garage for the winter (so that birds don’t feast on the pupae). In early spring, put the whole house inside of a cardboard box (here’s an image of durable emergence box). Poke a small hole in the top or side so that emerging bees see the light and escape through that hole, and then set it outside in a place where it will stay dry. After all the bees finish emerging (summer), throw out the house. Or, better, burn it and record a video of the fire. Then post the video online to bring needed awareness to low quality mason bee houses. If you have a good photograph of a burning mason bee house, I could use one right here.

“I want a cute bee house but not the commitment”

If you absolutely want the cute look of a bee hotel but don’t want all the maintenance fuss, here’s a trick: print this photograph onto a large piece of paper and mount onto a board. To make it last, laminate or apply a coat of clear varnish.

Question?

If you are about to buy a house but are nervous it’s death trap, email me a pic.

Don’t let the above discourage you from owning your dream house: here’s a draft listing of companies that make good ones. Or, make your own.