Yes, you will decide. We don’t know what your yard looks like or what you have planted. You may live in a higher elevation. Use the two criteria below to decide when to put out cocoons.
Weather in the Willamette Valley still has the potential to have a cold spell and heavy rain. For a better outcome waiting until Mid-March is a good way to go. Look at your yard and use weather indicators to decide when you will put out your cocoons.
Criteria #1 - What is blooming in your yard?
If you have very few flowers blooming yet, you need to look for near-by Big Leaf Maples and Willows to see if they are generating pollen. This pollen is especially important until enough flowers are blooming to support the bees. You will have to decide if there are enough plants and trees blooming to provide the bees with pollen and nectar. The mason bees need a continuous source of food. Plan ahead and add more native plants too. Because many hybrids do not produce nectar or pollen, they have no food value for bees.
Criteria #2 - Watch The Weather
In mid to late March, look at the long-term forecast to see that there is no heavy rain forecast. Then you can start thinking about putting out cocoons. We should have at least three days in a row of 50 - 55 degree weather to be warm enough for the bees to emerge and survive. Yes, it has been that warm recently, but heavier rain is still very likely. Waiting just gives the bees a better chance.
Once you have blooming trees/plants and warmer weather without heavy rain forecast, you can put your cocoons in your emergence container. A good container is a 5-inch length of PVC pipe that is 1-inch in diameter, with caps on each end and 5/16” drilled in one of the caps. Don’t stack the cocoons more than 2-3 layers high if you are using another type of container for the cocoons. If you have lots of cocoons, it is better to use more emergence tubes and also to put out more houses. Try to not have more than 50 or so nesting holes in each house. You will have less pest issues if you keep the number of holes in the 50-ish range or lower.
Note: Our guidelines are tailored to the Willamette Valley of Oregon. We want blue orchard mason bee cocoons that you purchase from us to be used within the east to west boundaries of the Coastal Range to the Cascades. The northern boundary is the Portland/Columbia River areas and southern boundary is the Umpqua Valley area. Check with your county Extension agent if you live outside these areas.