I am also in colorado and had the same on my plants last year but about half the size. I have no idea what it is. I peeled a piece of it off and it did not look like any type of bug. The "bark" or outer layer of the stalk came off with it. I remember that they dont move at all. Just grows.
Looks like some sort of a Gall to me, they can be caused by a bunch of different types on insects and are the only things I can think of that would cause growths like that. You could probably slice one open and see what kind of larva is incubating inside