Yes, those are mason bees. Congratulations!

They don't need water, but they do need mud to build their nests. Also, to keep them going over time you will need to harvest the cocoons (inside the reeds) come fall. Generally, harvesting cocoons in bamboo is almost impossible, so next year you might consider using cardboard straws with paper linings, or wooden blocks that enable cleaning.

Encouraging mason bees

Here are a few tips on how to grow the number of bees you have over time.

  1. Access to mud: I know it's been wet, but the bees need a continuous access to wet clay. This can be facilitated by digging a small hole in the ground and covering it with some plywood propped up (to prevent drying out) with gaps for the bees to get in on the edge. Keep this wet through the nesting area and make sure it's relatively close to where the nests are.
  2. Plants need to be flowering when the bees emerge: You will need early flowering plants that are already blooming as the bees emerge. Great late winter shrubs include rosemary, willow and Oregon grape, followed by any of the fruit trees (including wild cherries) and California lilacs (different from ornamental lilacs, which they don't use as often).
  3. Staggered release: After you harvest cocoons in the fall (and I would recommend you take a class from our Master Gardeners) you can help boost your returns with a staggered release. You see, after you harvest your cocoons, you can store them in your refrigerator in the winter. Then, you can release a few at a time, ensuring, if the bees hit a stretch of bad weather, your next batch will have better conditions.

I would also recommend signing up to the Linn County Master Gardeners Bee Notes, which provide timely recommendations for mason bee culture.

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