Mason Bee Blocks

I found a cute little video about “solitary bees” online today.  It shows a design I haven’t seen before.

I don’t like that it’s hung like a bird feeder instead of firmly attached, but it’s cute.  It’s also the paper tubes that I’m never going to use …  Well, it made me think about bees again anyway.

Mason Bees

Around here we have mason bees (Osmia lignaria). If you see them, you might think they are flies rather than bees. These innocuous little bees work hard to pollinate our spring flowers and fruit trees. They deserve a good place to have their young.

It happens that it’s exceptionally easy and cheap to provide accommodations for them! September is not the perfect time to put up a bee block/”bee hotel”.  But you might have time over the winter to MAKE one, so here goes.

Your nest can be a simple block or a half-round log with a roof, or you can build one that looks like a birdhouse, or you can paint the roof to make a charming folk art nest block, or…  The sky is the limit! Do some research or use your imagination and come up with something that suits you.

You can get your kids/grandkids involved too. It’s a great project for them to participate in. They could drill, decorate, or hang. And they can help you keep track of how many holes are sealed up every year, and watch the bees emerge in the spring. It could be a great Christmas project too — a useful home-made gift for the person who has everything.

Mason Bee Blocks

DO NOT USE TREATED WOOD.  You likely want softwood, because you’ll be drilling a lot of holes. Pine or spruce is fine.  (Agriculture BC says no cedar because it repels insects, but I’ve seen bees checking out the countersunk screw holes on my cedar deck chairs. They didn’t seem repelled. Your call.)

Ideal dimensions:

  • Space the holes ¾ of an inch apart.
  • Make holes 5/16 inches (7 to 8 mm) in diameter.
  • Make holes about 6 inches deep.  Do not to drill all the way through.

In a pinch, make the holes at least 3 inches deep, and 1/4 inch to 3/8 inch in diameter. Holes that are shorter than 3 inches deep and small diameter holes encourage the laying of males, which are not as beneficial as females.  (Sorry guys!)

I don’t think that the number of holes matters a great deal.  (… the allure of my cedar lawn furniture.)  I think they just want a nice deep hole, period.  You could start with a 6 inch or foot long section of 6 by 6, or a log and see how that works. (A 4 by 4 drilled almost through will also do in a pinch.)

Do not varnish or paint the INSIDE of the nest holes.

You could char the outside of the block.  Darker wood is more attractive to bees.

If the place it will be mounted doesn’t provide rain shelter, you might want to make a wide roof for your block.  And you could use a screen of wire mesh (no finer than the drilled holes) to  protect the nest block from foraging birds.

Slot the back of the block for hanging.  OR use a (~) 4 inch by 4 inch board about 1/2 an inch thick screwed onto the top back of the block to mount the block. (Two screws to attach the bottom half of the board to the block and two screws to attach the block to its support.)  OR you could just angle two screws through the top of the block to mount it.

(Note that there are many other ways to make bee blocks.  One method uses paper sleeves like the ones in the video above.  Some people go to the trouble of bathing their bees to remove mites and storing them in the fridge.  I’m never going to do that.  It’s even less likely than me ironing clothes.  🙂  But feel free to check it out via web searches if YOU want to do it.)

Replace the nest block every one or two years — in early March or when the current occupants have hatched.  (If some holes are “occupied” by the time you get to it, you can cover the unfilled holes or fill them with a nail.)  Pathogens will build up if you leave the nest block up indefinitely.

I would replace it every year, just to be safe. Or you can research ways to clean and re-use the blocks. Just keep in mind that you don’t want mould, parasites or chemicals to impact your bees.

Mounting the Block

You can attach the block to your shed, your house, a fence post or even to a tree. You want to make sure the wind can’t blow it around. Firmly mount the nest block at least 3 feet and not more than 6 feet above the ground.

Winter wind/rain protection is key. Ideally, you can mount it on a sheltered southeast to east-facing site (to receive morning sun in the spring). That’s why it gets a bit complicated where I live.  The prevailing winds in the winter are from the southeast — often driving the rain pretty much horizontally.  In this case we can either shelter our bee block elsewhere for the winter OR we can mount it out of that wind and not give the bees the morning sun. (It won’t matter if they receive morning sun if they haven’t survived the winter wind and rain.)  If the blocks are relocated for the winter, make sure they are protected from heat, predators, etc. Don’t bang the block around.  Be very gentle so that you don’t disturb the larvae in their feeding. Put the block back in its optimal position in late winter — when the native flowers and fruit trees begin to bloom.

What else can you do?

Bees need a mud source and a water source. (Butterflies too!) They use the mud to make the little plugs you will see in your mason bee block — hence “mason” bees, eh.

You may have heard that our bee populations are in trouble. Helping these little bees is a simple way to help save our one and only planet.  I hope you will give it a try.

Check the library or the internet for more information on mason bees, or for information on the solitary bees in your area.

Check out my website at

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