One of the mistakes beginning mason bee keepers make is that they forget (or don't know) to harvest bees in the fall. If you let bees survive on their own, mite infestation occurs and you begin to lose more bees than you started with.
That's why bamboo isn't a great nesting reed. It's too strong and can't be opened without killing the bees.
Reeds, on the other hand are awesome... unless you leave the bees on their own.
Why manage bees? It's the same thing as managing cows or sheep. If you don't care for them, pests/disease overrun.
Owner, Crown Bees
Think outside the hive, raise native bees
You could try Japanese Knotweed. It's invasive and spreads fast, but you'll get a lot of tubes really fast. I have a small patch (50 square feet) that I harvest once in the spring for food, then cut a few times a summer for a compst additive and then a final cut in the fall to dry and use for next years mason bees. Each successive cutting produces narrower diameter stalks. The early summer ones are about an inch while the fall ones are closer to a quarter inch or so. Once dry I store them in the basement till after the wet spring then just pile them up in a dry area.
Here's another idea for "reeds"... the dried stems from Jerusalem Aritchokes.
I had a bundle of them on the porch for a fall/halloween decoration.
After cutting them to size, and cleaning them out with a wire they look just perfect.