After a dinner at a community hall one year, I wandered through the surrounding garden and I was delighted to see this crab apple tree with all its fruit. Since it was fall and all the leaves had fallen, these pink crab apples, small and large, made a showy and colourful picture. Because I studied pollination and pollen loading of blueberries, I was off course interested to having a second look at the pollination of this tree. I wanted to see if there were any patterns of where the large and small apples were located on the tree. One pattern was very clear and can be seen in this photo. The more accessible flowers on the outside of the canopy produced larger fruit. This means that flowers on the outer canopy received more bee visits because more pollen was deposited on these flowers. The lesser accessible flowers on the inside of the canopy are small and received fewer bee visits. Flowers close to the ground also produced small fruit.
This tree did not receive optimal pollination. If the plant is healthy, the two major reasons why poor pollination occurs is insufficient bees or poor weather or a combination of these two factors. If poor pollination occurs in good weather, then insufficient bees is the more likely reason for poor pollination.
People often ask me how many mason bees must a garden have for good pollination. Fruit production is a great way to tell if good pollination occurred during the previous spring. If pollination is good for a series of 3-4 years, which includes a poor weather year, then sufficient bees are in the orchard.
Lack of good pollination produced both large and small crab apples.
After our trip through Saskatchewan, the idea of a workable yurt for mason bees began. I was fascinated by the roof opening and how it apeared to work nicely with alfalfa leaf cutter bees. Since leafcutter bees and mason bees are in the same family a yurt like structure might just work for mason bees.
I had one experience with leafcutter bees that did not work very well at all. But I did learn from the experience.
I built a U-shaped structure using regular poly on the surrounds. The roof was made of solid wood. The open part of the ”Ú’ acted as an open door. Bees emerged and started nesting. After a couple of days, I was back and to my dismay, the leaf cutter bees were getting caught between two layers of plastic stapled to the wooden uprights. The stapling kept the plastic on the structure, but if a bee became disoriented, she would fly agains the poly and then over time end up between the overlaid plastic walls. Many were caught. I removed a lot of them by cutting the plastic, but this let the wind in and ….basically this structure did not work at all.
The yurt cover is made from one piece sewn together to form a snug fit. If a bee does get disoriented in a yurt, she ends up flying out through the roof, and back into the yurt via the door. A great solution for disoriented bees.
Yurts of all colours in the distance.
These prairie yurts make pollination feasible since leafcutter bee nests are protected from the wind and rain. Temperatures inside the yurt are warm under windy conditions and on very hot days, excess heat escapes through the roof. It seemed that this structure moderated both cool and hot temperatures.
We saw two designs that consisted of a metal framework and surrounds of tarp.
The metal framework consisted of one inch square tubing, welded together into a Octagon.
In this yurt, the roof consisted of 8 metal bars, bent to make a sloping roof. Note that the tubes leave an 8″ diameter hole in the roof.
I found out later, that these very heavy structures were left in the field all year round. Of course the tarp was removed when nests were removed. Sometimes fields of alfalfa are burned with the metal part of the yurt still in the field. Because of their weight, you would need a good size truck and some kind of a lift to haul them onto the truck.
I thought this would be a good system for farmers who have heavy duty equipment, welding capabilities and large acreages to pollinate.
But a structure is needed so that small operators with a few thousand mason bees or more can be more successful in gardens and small orchards.
The tarp was held onto the frame with plastic ties threaded through tarp grommets.
Most of the leafcutter bees flew through the door opening, but a few, perhaps the disoriented bees, exited through the roof.
Even with a stiff breeze, it was nice and warm inside the yurt. Not too hot, like the plastic molded yurt.
Since that time, we have tried quite a few different designs using different materials. We do know that we are sticking to tarp material. Tarps work and are readily available. More on some of our designs in the next blog.
The framework of this yurt consists of 8 pieces of metal. These are welded together using a center ring. There are 3 alfalfa leaf cutter bees visible flying through the roof -vent hole.
A plastic tie used to hold tarp to metal framework of the yurt adjacent to door.
The first time I saw yurts was in 2005.
Strange structures in a prairie alfalfa field
In 2005, we travelled across Canada for a holiday. While we were travelling through Saskatchewan, I saw these strange structures in alfalfa fields. I guessed that these structures could be housing alfalfa leaf cutter bees used to pollinate alfalfa for seed production. A few years prior to this, I had seen wooden sheds, crates and empty buses used to house alfalf leaf cutter bee nests. We looked inside and saw that it did house leaf cutter bee nests. However, even though there were quite a few small vent holes and an open door, it was very hot inside. This yurt was molded and made of plastic.
Molded yurt for housing alfalfa leaf cutting bees
Styrofoam alfalfa leaf cutter bee nests hung from the walls of the molded yurt
A emergence tray of loose alfalfa leaf cutter bee cocoons.
Colourful yurts made of tarp material were also seen. The roof was made out of translucent white tarp and the wall was either made of white, orange or blue tarp.
Yurts made of tarps in the distance.
Tim is having a closer look at a tarp yurt in a blooming alfalfa field.
When we stepped inside, the temperature was probably around 25C. Not too hot and just right for alfalfa leaf cutter bees. Alfalfa leaf cutter bees need at least 20C. I thought that this yurt design was much better than the molded yurt. The temperature inside the yurt was just right for these bees. The only difference that I could see between the tarp yurt and the molded plastic yurt was the larger roof hole in the tarp yurt.
…More on this design next time.
Thank you for your feedback, comments, great ideas and questions. If you have any pictures and or stories about mason bees to pass along to other readers, email them to me and I will post them.
This white Rhododendron provides valuable pollen and nectar supplies for mason bees. Unfortunately not all rhododendrons provide food for bees.
One of the bloggers-Steve suggested using a large (garbage pail size) plastic container for holding nests. I tried this type of structure when I was using nesting straws. The container was set up on a framework above the ground and on its side. We cut a few holes for venting water vapour through the roof (base of container). We also cut a few holes into the plastic at the entrance because bees would get caught in the puddles in the rim and drown. Nest would first be completed and filled in the upper sections (where it would the warmest) and slowly the lower nesting tubes would be completed. The system worked for a couple of seasons until we moved onto nesting trays. Square blocks are more difficult to arrange into a round structure and we needed larger structures to hold many nests. Sorry Steve. I dug around for a few photos, but I think they were pre-digital. I will dig them out at some future date.
A mason bee on a cabbage flower.
Our first yurts were made out of wood. and the nests were set up inside the yurt.
Quicklock trays set side by side on wooden boxes inside the yurt
In the early 1990’s at the beginning of my research on mason bees, I read numerous papers on mason bees. Many of them were authored by Phil Torchio and published in the1970’s. What I could not work out immediately, at the time, was why after all this research, were mason bees not available by the billions for pollination crops and home gardens. There must be something I am missing. In about 4 years I had over 20,000 cocoons and set them out in blueberry fields.
Since there are is no protection from the weather in blueberry fields, these open sided boxes were set out with about 20,000 mason bees. Each structure contains about 600 nesting tunnels in highrises or stacks of 72 nesting holes. The nests are oriented in slightly different directions to assist the returning bees finding their homes. The coloured plastic was placed in the ground and used as protection against the rain and also used as orientation cues. The wooden structures were set up on totes to get above the splash zone.
Bees will forage and pollinate any flower that has food for them. Plants that produce lots of nectar and pollen are preferred over others. This is a cabbage flower.
If my increase in mason bees over four years is a normal increase in numbers, I should have bees by the billions. I don’t.
We know that if parasitism and predation gets away from you, numbers of cocoons produced can drop dramatically.
But there are other factors.
Food availability is a non- brainer. But it is difficult to assess if the quantity and quality is out there for our mason bees. Seeing flowers is one thing, but knowing the quality of the pollen is another. We usually assume lots of flowers means lots of food.
All these factors are important, but nothing works if the weather does not cooperate.
So making a structure that keeps the bees warm and out of the rain and wind, makes a lot of sense. It is not only important to keep the nest warm for the adults, but for the developing young as well.
The open wooden structures (as in picture above) were unwieldy and protection from the weather was minimal altough sufficient if the weather was sunny!
The Gazebo for mason bees was born. More next time.