The needs of native bees are simple: food and a home.
Depending on the bee, the requirements for a home differ, of course. For example, ground-nesting bees need different materials than twig-nesting bees. Below, we list a few ways you can provide nesting resources for the cavity nesting bees like mason bees (Osmia) and leaf-cutter bees (Megachile).
Build a bee block.
· Use a piece of untreated lumber, it can be any size, but five to nine inches long by three to five inches wide is good.
· Drill holes between 1/4th and 1/2 inch, about 1 ½ and three inches deep (respectively, smaller holes should not be as deep). Several can be put in one block of wood, place them about an inch apart.
· Mount the block on a post, and place a ‘roof’ over the top so that rain can’t fall directly into the bee nest holes. Keep the blocks of wood off the ground just a little, to prevent extra moisture from seeping into the wood, and to minimize attack by ants and other non-flying enemies.
· Turn your nesting blocks so that they face south or south-east. On cool days they will warm up earlier and your bees will be able to start gathering pollen.
· Move your bee nests into a protected place for the winter months. You can move them, either to a shed, or an unheated garage, or just cover them with a tarp. If you choose to move them, wait until early November. Many wood-nesting bees emerge in the spring; consequently they overwinter as adults. These bees pupate, and are in their adult form by late fall. In this state they are much more stable and less inclined to suffer from the jostling that would come from moving their nesting blocks earlier. Don’t forget to move the blocks back in the early spring.
· In areas of the southwest, adobe blocks can similarly be used. Drill holes in the adobe brick just as you would a piece of wood.
Build a bee nest bundle.
· Instead of drilling holes into a piece of wood, you can provide pre-made tunnels for twig-nesting bees.
· Cardboard straws, either prepackaged in a ready-made container and purchased from an insect supply store, or singly, can be purchased.
· Alternatively you can tie together bundles of hollow elderberry stems, pieces of bamboo, teasel, reeds, yucca stems, or other hollow stemmed plants. Roughly one to two dozen stems can be placed in a bundle together.
· The length of the straws should be roughly six to nine inches in length, and it is important that one end of the straw is closed. Ideally, cut your natural stems just below a node, so that one end is naturally sealed. Otherwise, a small dollop of caulk will work.
· Straws can be stuffed inside a piece of 2 or 3 inch PVC pipe with one end capped. Don’t be surprised if some bees nest in the spaces between your straws too!