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Mason Bees- Why No Holes or Few Holes Plugged?

We always get calls and emails from our hosts regarding holes being filled. We know it can be very disappointing when the bees don’t fill many holes, but we want to reassure you that you’ve still impacted solitary bee populations and helped your habitat. Since solitary bees are such incredible pollinators, when you released them into your yard you helped create a healthier ecosystem by strengthening your trees and flowers that will provide cleaner air, stabilize soils and support other wildlife. You’ve also helped grow the local population of solitary bees, which are commonly eliminated or reduced from urban areas as they are being develop.

If you had clay or clay-like soil, didn’t use pesticides, hung your house in a sunny spot and had a lot of flowering blossoms in the spring then you created a great habitat for mason bees. Rent Mason Bees and all pollinators THANK YOU!

Now the fun, science and research part. One good indication that the bees have emerged is by spotting the tan-colored markings that they leave on the outside of the white emergence tube. Do you see any markings?

The second study is to examine the cocoons in your white PVC tube. Grab a paper towel or a piece of white paper and dump out all the cocoons in the tube. Examine each one. Are the cocoons empty? Did any bees not emerge? Feel how strong and durable those silken cocoons are. What else did you find? If the cocoons are empty then you know all those mason bees flew off into your yard and pollinated and enriched all the trees and flowers and you gave back and helped the mason bee population.

In the fall you’ll mail back your nesting block, whether it was filled or not, and we’ll sterilize it and clean it to get it ready for next season. Make sure you keep your black house and next year you’ll just need to order a new nesting block insert that comes with new bees.

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Reader Interactions


  1. keith says

    I have two bee hotels made from old 4×4″ fence posts cut offs about a foot long drilled various sizes approx 30 in total and witnessed the bees VERY busy last year, most of the holes plugged with mud ! as of now no bees have emerged with the plugs in intact just wondering why this as happened

    • Thyra McKelvie says

      Hi Keith,
      Here is a video about the proper nesting material to use for solitary bees. Logs with holes drilled in it can’t be cleaned and over time they will become a predator habitat.
      Nesting material is not left out year round… it needs to be removed in June and then opened and cleaned in the fall. New nesting material needs to be placed out every spring.

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Bee Amazed

Mason bees
visit up to
flowers a day
400 Mason bees
do the work of
honey bees
One Mason bee
block can hold
bees per acre
to pollinate their