Leaf Cutter and Mason bees are Northwest native bees that have several characteristics different from Honey bees. These wild bees are solitary and have a mild manner, they rarely sting. They live in small round straw-like cavities (not hives). And they don't make honey.
Sometimes referred to as "pollen bees" these natives have a short lifespan that is devoted to collecting pollen. That's why they are so beneficial to your garden!
Because Mason and Leafcutter bees don't have pollen pockets like Honey bees, they leave more pollen behind so they're more efficient pollinators. Typically Mason Bees pollinate 95% of the blossoms they visit (compared to 5% for Honey bees).
Mason bees are early spring pollinators and typically the first bee in your garden. They're also referred to as Orchard bees because they are active when fruit trees are in blossom.
Plants that Mason bees especially like include: crabapples, redbud, flowering currant, elderberry, huckleberry, Oregon grape and lupine.
Leaf Cutter bees are summer bees, they become active in late spring through summer. They are named because they cut away small pieces of leaves, which does no damage to plants.
A native bee nest is easy to create in your yard. Choose a location that is several feet above ground and under an overhang. Swarm's native bee nests are made from sustainably harvested cedar that is weathered for a coulee of months. And the nests have cardboard tubes because they are easy to peel back in the fall to collect dormant bees, which is the best way to ensure their survival over winter.
Order Swarm's hex nest here: https://swarmportland.org/collections/garden/products/native-bee-nest
It's possible to attract wild bees if you provide nests, or you can purchase bees in cocoons and place them in the nests. Many local nurseries sell Mason bees, and the time to act is when the temperature stays above 50 degrees. Leafcutter bees are available in late spring and remain active through summer.
The Xerces Society has more detailed information on proper care for native bees: http://www.xerces.org/wp-content/uploads/2009/11/tunnel-nest-management-xerces-society.pdf
Pesticides harm bees so don't use them if you want a pollinator-friendly garden.
Additional information: http://extension.oregonstate.edu/gardening/2015/04/efficient-mason-bees-pollinate-plants-honey-bees-get-busy