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Mason Bees- Why No Holes or Few Holes Plugged?

Mason bee season has come to an end and we want to thank everyone who hosted with us. If you haven’t already, you can carefully remove your nesting block and store it with the holes upright in a cool garage or shed. This will protect them from mono wasps and other predators. If you hosted from us, PLEASE DO NOT MAIL BACK YET… we’ll notify you in September when it is time to send your blocks back. At that time we will harvest all your cocoons, clean the bees and sterilize your nesting blocks for next season.

So, let’s talk about holes filled. 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!

So, if you didn’t have any holes filled, let’s do some fun math to show you what happened in your yard!! The bees you released didn’t fly far from home and found other holes in your yard to lay their babies (one even laid eggs in my deck umbrella).  You released about 60 bees and each mason bee lays about 15 eggs. That means 900 babies will hatch next spring!!! Yes 900!!  So you just helped native solitary bee populations. Even if you have one or two holes plugged, each hole plugged has about 7 babies in it!!

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 the kids and a plate 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. Then, all those babies that are now in your yard may choose your nesting block and repeat the cycle of life all over again.
We had a little science fun ourselves. Over the course of two months we opened up our mason bee nesting block to show all of you what your baby bees look like and how they develop. PLEASE DON’T OPEN YOUR BLOCK, otherwise your bees will get damaged in transportation. We did this for you and it was fascinating to see their development and also learn about some of the predators and other things we found in our nesting block.

We hope you enjoy our 3 part series of


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Bee Amazed

Mason bees
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400 Mason bees
do the work of
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One Mason bee
block can hold
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to pollinate their