Very nice video, John!  I kept mason bees about a dozen years ago but haven't actively done so since; I'll occasionally see a solitary one around so at least they're still present.  I wouldn't have thought to use teasel stems.  Fortunately we don't have any on our property, but about 2 miles away there's an empty lot right next to the Newaukum River that is so dense with them every year that one would think it was being grown commercially.

If you have any elder plants around you could also cut selected stems from them.  They normally have a pithy core in a fairly sturdy woody cover (when dried) and could easily be drilled out.  Different diameters could be selected for different bee species.  Sometimes carpenter bees will even burrow-out the pith on larger diameter dead branches of elders for "nesting".

Good idea too on increasing the number of umbellifers to attract pollinators.  I'm gradually increasing the number and variety of Compositae, Umbelliferae, and Labiatae (aka Asteraceae, Apiaceae, & Lamiaceae) around our yard with the native bees and bumblebees specifically in mind.  We have a nice diversity of native bees on our property, but in the absence of a good quality dissecting scope I'm not yet able to key them out to family, genus, and species.  Just want to keep them all healthy and present, though.

Tim.

I took some video of my mason bees this morning.  I had a bunch of cleaned cocoons in the refrigerator.  Within minutes of removing them from the refrigerator they started hatching, so they must have been quite ready.  Unfortunately I don't have any apples blooming yet.

I went out to place the cocoons in the pots where I have teasel & bamboo stems, and I found dozens of males frantically searching for females.  However the girls haven't woken up yet.  

Within a minute there were males crawling into my container of cocoons.  So apparently they can smell each other.

The bamboo that you see in the video is what I use for stakes.  I would have thought these were too big for the bees to use, but I guess not.  Sorry I didn't get any video of my tube bundles.

I did have an aha moment today while putting teasel stems into plant pots which I have screwed into the wall of the tree house.  The stems tend to fall out of the pot easily, especially during heavy wind (the pots are semi-horizontal, pointing slightly downward so they can drain).  I discovered today that if you put a flat rock on the top of the stems, it keeps them in place.  In the past I have tied them into bundles with string or wire, but that is tricky, and it is hard to make bundles the right size to fit into my pots.  Also in the fall when I go to open the stems, the bundle falls apart when I start removing tubes from it.