Mason bees could be the most remarkable insects in the garden. Native to most parts of the country, they are quite passive; the males have no stinger, and the females sting only when severely threatened. They are major pollinators; some say one mason bee does the work of 500 honey bees. Unlike honey bees that only carry pollen on their hind legs, mason bees are covered in it as they do their work collecting pollen. Less than 10 mason bees can fully pollinate one 15-foot fruit tree. Mason bees have mostly flown under my garden radar, but as soon as I began studying them, I fell in love. I wanted to see what I could do to be a friend to the humble and magnificent mason bee.
The life of a mason bee could be the plot of an opera; they live short, solitary lives of service to the next generation. If you’re a male, your sole purpose is to procreate. You are born before the females and can often be spotted waiting outside the nest for a mate to emerge. Once you have done your duty, you die. If you are a female, you are born to make babies. The process begins once you emerge from your cocoon. Once the deed is done, you disappear for a few days while your ovaries mature. Then begins the arduous process of many trips of collecting mud to build the next, gathering pollen and nectar, and then laying your eggs. Soon you will also be dead. But in a matter of a month or two, you make an enormous mark as you pollinate many blossoms and build a brood for the following year.
Mason bees build their nests in narrow (around ¼-inch in diameter) tube-like openings like hollow stems and burrowed holes in the wood from other insects. Their nest is an architectural feat. They seal the ends of their nest and build the chambers within from the mud they collect; thus, the name mason bee. In each chamber, they vomit nectar and deposit pollen they’ve carried to create what is called a loaf. The egg is laid in the loaf, and the wall is built with mud to seal it off. Each egg has its own larval cell, and the entire affair is sealed at the entrance. The structure resembles one of those compartmentalized pill boxes with the day of the week on each segment.
Mason bees are intelligent. Female eggs are laid at the back of the nest, where they will be safe and less vulnerable to predators. Male eggs are laid near the front of the nest.
In a couple of weeks, the larva emerges and feed off the pollen and nectar loaf. When the loaf is gone, the larva forms a protective cocoon around itself. After several months of dormancy, the larva develops into a bee but remains in the cocoon throughout the winter. The mason bee will emerge from its cocoon when daytime highs average in the mid-50s several days in a row.
The bee house: to be or not to be
How could one not want to help this unsung hero of the garden? Bee houses are little human-made structures designed to give the mason bee (and other solitary bees, like the leaf hopper) a place to build their nests. Bee houses are, in a word, cute, and can be found all over these days in stores and online. Pollinator enthusiasts are clamoring for them. The jury seems to be out for pollinator experts.
Our hearts are certainly in the right place when we set out to provide a home for these highly beneficial members of the garden community. We want to be a part of the solution, plus mason bees near our fruit trees can mean more fruit. Many of the ready-made bee houses are reportedly not right for the bees. Nurseries, garden centers, and specialty stores are good sources; stores, where you can also buy dishes, candles and clothes, may not be. Some houses can even be harmful as they lure the bees away from natural habitats only to provide a home that puts them at risk of mites and other predators. Note: this can also happen in natural settings like holes in logs, and plant stems from the previous year.
If you build it, will they come? I confess—I am new to the world of the mason bee and the bee house. My knowledge on the subject is limited to my research (a pleasurable process). I’ve decided it’s worth embarking on the journey of creating a bee house for my new best friend in the garden and making it as safe and hospitable for the bees as possible.
My DIY Bee House
When building your own house, there are a few must-dos that reportedly many of the commercially produced houses do not follow:
- Do not use treated or even painted or varnished wood. The treated wood can be toxic to the bees, and the finished surface may deter them. Choosing a wood that is weather resistant like cedar, is an option, though I happened upon a couple of bloggers who warned against cedar because of its natural scent. I used untreated pine, which is not overly durable to the elements, but bee houses are best placed in a sheltered spot, like under the eaves of the house, so this will help. The bottom line, bee houses are not permanent structures. I accept that I will need to replace mine in a few years.
- The house must have a back to protect the bees from predators. Constructing the house to have a removable back for cleaning is helpful. I screwed the back onto my house to allow for removal.
- Components need to be removable for cleaning and replacement, and not glued in place.
- Bee houses must be securely attached to a structure so they don’t sway or rock in the wind.
The basic structure
I built my house using a circular saw, a drill, and basic carpentry. My DIY motto is to do your research, do your best, and not get caught up in perfectionism. Getting something done is more important than being perfect. Please review my plans, replicate what you like, and experiment with crafting your design. Additional information and accounts of tending mason bees are endless online.
The base structure of my house is a total of five boards, ¾-inch thick, in the following dimensions:
- 2-12×7″
- 2-10×7″
- 2-9×7.5″ w/ 45-degree edge on one end (for the roof)
- Various 10″ wide boards to cover the back
I built a box with the 12 x 7″ and 10 x 7″ boards, using 1 ¼-inch coated screws for weather resistance. I attached the roof with 1 ½-inch screws. I pre-drilled pilot holes for the screws to help keep the wood from splitting and to go in easily.
The roof is attached by screwing the two angled ends of the 9 x 7.5″ boards to form a V. I then placed the inserted V onto the top of the box and screwed the bottom edges into the box. Next, I screwed three 10″ long boards of varying widths onto the back and cut a triangular piece to cover the back of the “attic.”
A woodworking note: I’ve built a simple homemade jig to make screwing two wood pieces together to form a right angle easier. Mine is just a piece of 1×6′ wood screwed into a length of 1×10′ wood.
Filling and hanging the box
Filling the box with nesting materials is the most important step in the process. Mason bee nesting tubes are readily available by doing an internet search. Tubes for mason bees need to be at least ¼-inch and no larger than 5/8-inch. They must also be six inches long. They should not be plastic. I purchased tubes with a replaceable inner lining as the cleanliness of the house is essential.
You can also drill ¼ and 5/8-inch holes in wood blocks that not all bee enthusiasts are in love with, but they look very cool. A bee house with a variety of materials is a good look! I recommend a 10-inch long drill bit for drilling into the wood. Drilling six-inch long nesting holes is not simple, but you can do it if you stop two or three times per drill to clean out shavings. Once you’ve drilled the hole, reinsert the drill bit and run it in and out a few times to ensure the sides are completely smooth. You can also insert paper tubes into the drilled holes, but I am trying it without them. A segment of tree branch is a natural and attractive addition. I used my small electric chainsaw to cut a six-inch length, then drilled holes in it. I used boxelder, which is a softer wood and easier to drill into.
Joe Pye weed is one of the plants bees will lay their eggs in the stems of. I harvested as many stems as possible from last year’s growth, trimmed them to six inches, and placed a bundle in the house.
Bee houses need to be stably hung at around six to seven feet off the ground. A south-facing location will help the sun keep the warm over the winter. A+ if you can place it under an eave for added protection.
Overwintering the box of bee babies
Many bee enthusiasts gather tubes in the fall and overwinter them in a protected area. If you choose to go this way, there is a lot of information out there to guide you. I am going with the easier approach and letting the house overwinter where it hangs and then placing it in an emergence box when temperatures are nearing an average daytime high of 55. I’ll place the bee house in a cardboard box with a one-inch hole cut in one end. The bees will see the light and fly out but will not return. Once the tubes are empty, I’ll clean the box and rehang it to repeat the process.
Cleaning the house is an important step in the process. The paper tubes will be replaced. From what I’ve read, people will clean holes in wood with compressed air and the tiny brushes used to clean out reusable straws and water bottles. It seems the ultimate would be to have two houses, with one ready to hang as soon as the first goes into the emergence box.
I likely hung my box too late this year to get any nesters, though I have spotted the bees gathering nectar on a spirea shrub. Sometimes, the bees will not nest in the house or survive the winter. Some suggest moving the house to a protected spot, like the garage, for the winter. Like so many gardening activities, I will see how it goes and at the very least, I will hopefully give a nesting place to a few of these marvels of the garden.
Minneapolis-based Eric Johnson blogs at gardendrama.wordpress.com.