Mason Bees on the Homestead

Japanese Hornfaced Mason Bee
Japanese Hornfaced Mason Bee Sunning

In a classic case of “if you build it, they will come”, what I considered to be a failed Mason Bee experiment, nature has miraculously turned into a success story. In 2012 I built a Mason Bee house and installed it on the north side or our orchard. It’s in a great spot, south facing into the early morning sun with a commanding flight path of the entire orchard. I bought several “boxes” of cocoons from Crown Bees and installed them into the house early that April of 2012. I eagerly watched for their emergence as temperatures rose, taking almost daily walks down to the orchard. Weeks went by and…nothing. No emergence, no activity. Summer wore on and I still saw no activity at the house, and I knew if it hadn’t happened by now, it wasn’t going to. So I opened the house and pulled out my boxes of cocoons. I was surprised to find that all of the cocoons had indeed hatched, but the little mason bees must not have found the home to their liking, and moved on. Chalking it up to a habitat failure, I had been meaning to take down the house for the past 3 years until I was able to install earlier blooming perennials and a water/mud source for the bees. But in a rare positive example of procrastination, I left the house up – 3 years later, I’m sure glad I was lazy.

If you have fruit trees, Mason Bees are the preeminent native pollinator species. They are specifically adapted to emerge very early, long before honey bees, when certain fruit trees are beginning to blossom in early spring, like Cherries, Stone fruits and Apples. On the east coast, the prominent breed of Mason Bee is the Japanese Hornfaced bee (Osmia cornifrons). On the west coast is the Blue Orchard Bee (Osmia lignaria). They are a solitary and gregarious breed, meaning every female is a queen and they can all happily coexist in the same house. They are not a social breed like honey bees. There is no hive hierarchy, roles, or responsibilities. Just males and females.

Mason Bees do not make honey, which is a plus and a delta: they have nothing to defend, so they are very docile, requiring no special equipment. They will almost never sting unless seriously threatened. Also, people who are allergic to bee stings are typically not allergic to Mason bee stings, as a Mason Bee carries far less toxin (YMMV).

Japanese Hornfaced Mason Bees Emerging
Japanese Hornfaced Mason Bees Emerging

Mason Bees will out-pollinate Honey Bees in an orchard 10-to-1. Honey Bees have evolved to carefully collect pollen in pouches on their hind legs to be carried back to hive. They don’t like to lose any. Mason Bees on the other hand are less concerned about collecting pollen. They’re satisfied with whatever happens to stick to their hairy abdomens, and much of it falls off as they fly around. In a word, they are “sloppy”. This sloppiness, coupled with the fact that mason bees have erratic flight paths, often flitting from tree to tree, means they are a significant source of cross-pollination for species that require it, like apples. Mason Bees will purportedly visit 15 blooms a minute, and 60,000 blooms in their lifespan. Whereas honey bees wander off for miles in search of that sweetest of nectar, Mason Bees stay close to the nest providing reliable, local pollination. Honey Bees are also prima-donnas, huddling in the hive when it’s cold, in contrast to Mason Bees who are highly active in the cool weather of early spring, and will stay active until late in the day. Mason Bees are the workhorses of the pollinator community, but are typically under-appreciated because they don’t produce honey. A great resource for learning about Mason Bees, and other under-appreciated native pollinators is SARE’s “Managing Alternative Pollinators” (free eBook).

What I like about Mason Bees is that they can be treated like a “crop”: you buy (or attract) a small colony of bees, which lay 15+ eggs each in their nest. At the end of the season you can “harvest” the cocoons and put them in the fridge. Next spring, put them out and they emerge to repeat the cycle. This way raising Mason Bees is a lot like “saving seeds” – your colony will grow over time and is self-sustaining. All you have to provide them is a house, a source of mud, and fruit blossoms. The only downside is they can be “flighty”, taking off if they don’t sense fruit blossoms nearby, or not returning to your house of they find another, more convenient home. I have not actually done this cocoon collection yet, but I might try it this year.

Mason Bee House
Mason Bee House

My Mason Bee house contains a mixture of commercial cardboard tubes and Japanese Knotweed reeds. Commercial cardboard tubes are convenient and properly sized, but expensive. Japanese Knotweed is an invasive species in New England, but is a readily available source of free reeds. Each “knot” section acts as a rear cap and the reed can be cut to the ideal length of about 6”. However, the diameter of the tube is important: too small and the bees will ignore it. Too big and you’ll get a higher proportion of female to male eggs (optimal ratio is 2 males to 1 female). I size the reeds with a standard #2 pencil – if the pencil fits snugly in the reed, it’s good to go. Also note that the front of the house is painted blue. Studies have shown that Mason Bees are sensitive to this color and it helps them find the house more easily upon their return from foraging. The rest of the house is painted white to help reflect the sun and keep it cool. The front is covered in chicken wire to help prevent predators like woodpeckers, swallows, and squirrels from using the nest as a source of protein.

I’m really excited to see what happens this year with my Mason Bee house. I thought it was a failure, but it seems I’m doing something right. Let’s hope it continues!

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