Monday, July 3, 2017

Mason Bees and bee houses

bee house
As many readers may be aware, bee colony collapse is a serious concern and the honey bee population is declining rapidly.  While there is still debate about the cause, the result is the loss of important pollinators.  I recently learned that honey bees are not native to the US and that solitary mason bees are.  These small bees are the hidden gems that help to pollinate our gardens and fruit trees.  They are not aggressive and their sting is mild - more like a mosquito bite.
mason bee
I read up on how to encourage and support them and found that you can easily make or buy simple "bee houses".  The simplest house is made from any block of wood.  You drill a bunch of 5/16" diameter holes 5" to 6" deep and the bees will lay their eggs in these holes along with some pollen. The bees then seal the hole with mud (hence the name Mason Bee).  The eggs hatch into larva and then then dig their way out as mature bees in the spring.  Click the image below for more info.
bee larva and cocoons

I built several bee houses from scrap 4X4" lumber with a small roof made from asphalt roofing shingle.  The roof is needed to keep the rain off and away from the sealed chambers and should protrude about 2".  

The houses need to be securely mounted so they face southeast or due east to catch the morning sun, this helps the bees warm up and get going in the spring. A good location for the bee house is under an overhang and out of direct weather, but they can also be mounted to trees.  Bee houses should also be located close to a source of mud, so near open water or very damp ground is ideal.  Solitary bees have a relatively small range of only 100ft or so, so they also need to be near blooms.  They are very active pollinators for fruit trees and only a dozen are needed to pollinate a fruit tree, whereas the same tree might need over 100 honey bees to do the same job.

Commercial bee houses often use paper tubes that can also be replaced.  There are many designs, here is one example that uses bamboo tubes:
While bamboo may work, I have learned that a 5/16" diameter hole is the size that Mason bees prefer.  If the hole is too small, they cant use it.  Too big and they expend a lot more work to fill the walls with mud to get their preferred size.

Ready-made bee houses are affordable at around $20 and can often be found at garden centers and big box hardware stores or on-line.  I don't recommend commercial plastic bee houses, apparently bees don't like them.  Stick with basic wood houses.

You can also purchase cardboard tubes separately in bulk and make your own house.  Holes or tubes can be lined with parchment paper to make them re-usable. 
Three weeks after installing my first bee house in June I found 3 holes plugged up and a bee working on another:

This is a simple and inexpensive way to support bees.  I have several fruit trees that I value and hope to encourage and expand my local bee population.

Some useful links:

Also a search YouTube shows many videos about keeping Mason Bees.