With all the talk about the threat to our honey bees, it is easy to forget that there are many native pollinators that visit our gardens, like the orchard, or mason bee (genus Osmia). In the wild an orchard bee will find an existing hole in wood, fill it with nectar and pollen, lay an egg, and then seal it with a mud plug. The egg will hatch after a few days and eat the food left by the female, after which it will spin a cocoon inside the hole. It will reside there through the winter and emerge the following spring.
It is easy to build an orchard bee house for your garden to encourage these gentle, beneficial pollinators. Here is a rustic bee house I built in a couple of hours out of a scrap piece from a 4×4 cedar post:
Drill holes about 5/16″ in diameter and anywhere between 3-6″ deep (depending on the thickness of your wood). Do not drill all the way through the wood. It doesn’t matter how closely they are spaced, but it is easiest to drill if they are spaced at least 1/2″ apart on center. The “tin” roof was cut from some left over corrugated roofing ridge cap and, like the base, is merely decorative.
You can hang your bee house, or place it on top of a fence post, as I have done here. It is important to place the house where it will receive sunlight and warmth, particularly in the morning. March is a good time to put them out, before the bees have begun nesting. It may take as much as a season or two for the bees to find your house, but in the meantime, it is an attractive and interesting addition to your garden.